SEC Info  
    Home      Search      My Interests      Help      Sign In      Please Sign In

Idt Corp. – ‘10-K’ for 7/31/20 – ‘EX-101.DEF’

On:  Wednesday, 10/14/20, at 4:56pm ET   ·   For:  7/31/20   ·   Accession #:  1213900-20-31279   ·   File #:  1-16371

Previous ‘10-K’:  ‘10-K’ on 10/11/19 for 7/31/19   ·   Next:  ‘10-K/A’ on 12/22/20 for 7/31/20   ·   Latest:  ‘10-K’ on 10/16/23 for 7/31/23   ·   9 References:   

Find Words in Filings emoji
 
  in    Show  and   Hints

  As Of               Filer                 Filing    For·On·As Docs:Size             Issuer                      Filing Agent

10/14/20  Idt Corp.                         10-K        7/31/20  128:8.4M                                   EdgarAgents LLC/FA

Annual Report   —   Form 10-K
Filing Table of Contents

Document/Exhibit                   Description                      Pages   Size 

 1: 10-K        Annual Report                                       HTML   1.19M 
 2: EX-21.01    Subsidiaries of the Registrant                      HTML     38K 
 3: EX-23.01    Consent of Bdo Usa, LLP                             HTML     34K 
 4: EX-23.02    Consent of Grant Thornton, LLP                      HTML     34K 
 5: EX-31.01    Certification of Chief Executive Officer Pursuant   HTML     38K 
                to Section 302 of the Sarbanes-Oxley Act of 2002.                
 6: EX-31.02    Certification of Chief Financial Officer Pursuant   HTML     38K 
                to Section 302 of the Sarbanes-Oxley Act of 2002.                
 7: EX-32.01    Certification of Chief Executive Officer Pursuant   HTML     35K 
                to Section 906 of the Sarbanes-Oxley Act of 2002.                
 8: EX-32.02    Certification of Chief Financial Officer Pursuant   HTML     35K 
                to Section 906 of the Sarbanes-Oxley Act of 2002.                
15: R1          Document And Entity Information                     HTML     98K 
16: R2          Consolidated Balance Sheets                         HTML    149K 
17: R3          Consolidated Balance Sheets (Parentheticals)        HTML     57K 
18: R4          Consolidated Statements of Income                   HTML    115K 
19: R5          Consolidated Statements of Comprehensive Income     HTML     67K 
20: R6          Consolidated Statements of Equity                   HTML     92K 
21: R7          Consolidated Statements of Cash Flows               HTML    130K 
22: R8          Description of Business and Summary of Significant  HTML     81K 
                Accounting Policies                                              
23: R9          Revenue Recognition                                 HTML     79K 
24: R10         Leases                                              HTML     51K 
25: R11         Cash, Cash Equivalents, and Restricted Cash and     HTML     40K 
                Cash Equivalents                                                 
26: R12         Acquisitions                                        HTML     50K 
27: R13         Debt Securities                                     HTML     52K 
28: R14         Equity Investments                                  HTML     53K 
29: R15         Fair Value Measurements                             HTML     62K 
30: R16         Property, Plant and Equipment                       HTML     42K 
31: R17         Goodwill                                            HTML     41K 
32: R18         Other Intangible Assets                             HTML     45K 
33: R19         Other Operating Expense, Net                        HTML     43K 
34: R20         Note Payable and Revolving Credit Loan Payable      HTML     38K 
35: R21         Accrued Expenses                                    HTML     40K 
36: R22         Other (Expense) Income, Net                         HTML     40K 
37: R23         Income Taxes                                        HTML     69K 
38: R24         Equity                                              HTML     42K 
39: R25         Stock-Based Compensation                            HTML     57K 
40: R26         Accumulated Other Comprehensive Loss                HTML     45K 
41: R27         Commitments and Contingencies                       HTML     51K 
42: R28         Related Party Transactions                          HTML     45K 
43: R29         Defined Contribution Plans                          HTML     38K 
44: R30         Business Segment Information                        HTML     56K 
45: R31         Accounting Policies, by Policy (Policies)           HTML    143K 
46: R32         Description of Business and Summary of Significant  HTML     51K 
                Accounting Policies (Tables)                                     
47: R33         Revenue Recognition (Tables)                        HTML     62K 
48: R34         Leases (Tables)                                     HTML     58K 
49: R35         Cash, Cash Equivalents, and Restricted Cash and     HTML     38K 
                Cash Equivalents (Tables)                                        
50: R36         Acquisitions (Tables)                               HTML     51K 
51: R37         Debt Securities (Tables)                            HTML     53K 
52: R38         Equity Investments (Tables)                         HTML     53K 
53: R39         Fair Value Measurements (Tables)                    HTML     63K 
54: R40         Property, Plant and Equipment (Tables)              HTML     41K 
55: R41         Goodwill (Tables)                                   HTML     41K 
56: R42         Other Intangible Assets (Tables)                    HTML     45K 
57: R43         Other Operating Expense, Net (Tables)               HTML     41K 
58: R44         Accrued Expenses (Tables)                           HTML     40K 
59: R45         Other (Expense) Income, Net (Tables)                HTML     39K 
60: R46         Income Taxes (Tables)                               HTML     72K 
61: R47         Stock-Based Compensation (Tables)                   HTML     54K 
62: R48         Accumulated Other Comprehensive Loss (Tables)       HTML     44K 
63: R49         Business Segment Information (Tables)               HTML     53K 
64: R50         Description of Business and Summary of Significant  HTML     79K 
                Accounting Policies (Details)                                    
65: R51         Description of Business and Summary of Significant  HTML     48K 
                Accounting Policies (Details) - Schedule of                      
                weighted-average number of shares used in the                    
                calculation of basic and diluted earnings per                    
                share                                                            
66: R52         Description of Business and Summary of Significant  HTML     37K 
                Accounting Policies (Details) - Schedule of                      
                outstanding stock options excluded from the                      
                calculation of diluted earnings per share                        
67: R53         Description of Business and Summary of Significant  HTML     42K 
                Accounting Policies (Details) - Schedule of change               
                in the allowance for doubtful accounts                           
68: R54         Revenue Recognition (Details)                       HTML     40K 
69: R55         Revenue Recognition (Details) - Schedule of         HTML     62K 
                revenues disaggregated by business segment and                   
                service offered to customers                                     
70: R56         Revenue Recognition (Details) - Schedule of         HTML     66K 
                revenues disaggregated by geographic region                      
71: R57         Revenue Recognition (Details) - Schedule of         HTML     41K 
                deferred customer contract acquisition costs                     
72: R58         Leases (Details)                                    HTML     45K 
73: R59         Leases (Details) - Schedule of supplemental         HTML     45K 
                disclosures related to the Company's operating                   
                leases                                                           
74: R60         Leases (Details) - Schedule of supplemental         HTML     39K 
                disclosures related weighted average operating                   
                leases                                                           
75: R61         Leases (Details) - Schedule of aggregate operating  HTML     42K 
                lease liability                                                  
76: R62         Leases (Details) - Schedule of future minimum       HTML     54K 
                maturities of operating lease liabilities                        
77: R63         Leases (Details) - Schedule of future minimum       HTML     52K 
                payments for operating leases                                    
78: R64         Cash, Cash Equivalents, and Restricted Cash and     HTML     39K 
                Cash Equivalents (Details)                                       
79: R65         Cash, Cash Equivalents, and Restricted Cash and     HTML     44K 
                Cash Equivalents (Details) - Schedule of cash,                   
                cash equivalents, and restricted cash and cash                   
                equivalents                                                      
80: R66         Acquisitions (Details)                              HTML     43K 
81: R67         Acquisitions (Details) - Schedule of acquisition    HTML     42K 
                date fair value of consideration                                 
82: R68         Acquisitions (Details) - Schedule of impact of the  HTML     66K 
                acquisition's purchase price allocations on                      
                consolidated balance sheet                                       
83: R69         Acquisitions (Details) - Schedule of consolidated   HTML     66K 
                balance sheet and acquisition date fair value of                 
                total consideration transferred                                  
84: R70         Debt Securities (Details)                           HTML     39K 
85: R71         Debt Securities (Details) - Schedule of             HTML     56K 
                available-for-sale securities                                    
86: R72         Debt Securities (Details) - Schedule of             HTML     49K 
                contractual maturities of available-for-sale debt                
                securities                                                       
87: R73         Debt Securities (Details) - Schedule of             HTML     41K 
                available-for-sale securities, unrealized loss                   
                position                                                         
88: R74         Equity Investments (Details)                        HTML     62K 
89: R75         Equity Investments (Details) - Schedule of equity   HTML     53K 
                investments                                                      
90: R76         Equity Investments (Details) - Schedule of equity   HTML     41K 
                investments (Parentheticals)                                     
91: R77         Equity Investments (Details) - Schedule of          HTML     48K 
                carrying value of equity investments                             
92: R78         Equity Investments (Details) - Schedule of          HTML     40K 
                unrealized gains and losses for all equity                       
                investments                                                      
93: R79         Fair Value Measurements (Details)                   HTML     35K 
94: R80         Fair Value Measurements (Details) - Schedule of     HTML     57K 
                balance of assets measured at fair value on a                    
                recurring basis                                                  
95: R81         Fair Value Measurements (Details) - Schedule of     HTML     44K 
                assets measured at fair value on a recurring basis               
                using significant unobservable inputs (Level 3)                  
96: R82         Fair Value Measurements (Details) - Schedule of     HTML     44K 
                liabilities measured at fair value on a recurring                
                basis using significant unobservable inputs (Level               
                3)                                                               
97: R83         Property, Plant and Equipment (Details)             HTML     36K 
98: R84         Property, Plant and Equipment (Details) - Schedule  HTML     51K 
                of property, plant and equipment                                 
99: R85         Goodwill (Details) - Schedule of change in          HTML     48K 
                carrying amount of goodwill by operating segment                 
100: R86         Other Intangible Assets (Details)                   HTML     49K  
101: R87         Other Intangible Assets (Details) - Schedule of     HTML     54K  
                presents information on the Company's amortized                  
                intangible assets                                                
102: R88         Other Operating Expense, Net (Details)              HTML     39K  
103: R89         Other Operating Expense, Net (Details) - Schedule   HTML     48K  
                of other operating expense, net                                  
104: R90         Note Payable and Revolving Credit Loan Payable      HTML     45K  
                (Details)                                                        
105: R91         Accrued Expenses (Details) - Schedule of accrued    HTML     49K  
                expenses                                                         
106: R92         Other (Expense) Income, Net (Details) - Schedule    HTML     45K  
                of other (expense) income, net                                   
107: R93         Income Taxes (Details)                              HTML     63K  
108: R94         Income Taxes (Details) - Schedule of income before  HTML     44K  
                income taxes                                                     
109: R95         Income Taxes (Details) - Schedule of deferred       HTML     61K  
                income tax assets                                                
110: R96         Income Taxes (Details) - Schedule of benefit from   HTML     62K  
                (provision for) income taxes                                     
111: R97         Income Taxes (Details) - Schedule of U.S. federal   HTML     58K  
                statutory income tax rate and income taxes                       
                provided                                                         
112: R98         Income Taxes (Details) - Schedule of change in the  HTML     41K  
                valuation allowance                                              
113: R99         Equity (Details)                                    HTML     80K  
114: R100        Stock-Based Compensation (Details)                  HTML     83K  
115: R101        Stock-Based Compensation (Details) - Schedule of    HTML     68K  
                stock option activity                                            
116: R102        Stock-Based Compensation (Details) - Schedule of    HTML     56K  
                grants of restricted shares of Class B common                    
                stock                                                            
117: R103        Stock-Based Compensation (Details) - Schedule of    HTML     55K  
                grants of restricted shares                                      
118: R104        Accumulated Other Comprehensive Loss (Details) -    HTML     56K  
                Schedule of accumulated balances for each                        
                classification of other comprehensive loss                       
119: R105        Commitments and Contingencies (Details)             HTML     47K  
120: R106        Related Party Transactions (Details)                HTML     73K  
121: R107        Defined Contribution Plans (Details)                HTML     44K  
122: R108        Business Segment Information (Details)              HTML     36K  
123: R109        Business Segment Information (Details) - Schedule   HTML     62K  
                of operating results of business segments                        
124: R110        Business Segment Information (Details) - Schedule   HTML     46K  
                of net long-lived assets and total assets by                     
                geographic areas                                                 
126: XML         IDEA XML File -- Filing Summary                      XML    250K  
14: XML         XBRL Instance -- f10k2020_idtcorporation_htm         XML   1.65M 
125: EXCEL       IDEA Workbook of Financial Reports                  XLSX    152K  
10: EX-101.CAL  XBRL Calculations -- idt-20200731_cal                XML    214K 
11: EX-101.DEF  XBRL Definitions -- idt-20200731_def                 XML   1.16M 
12: EX-101.LAB  XBRL Labels -- idt-20200731_lab                      XML   2.12M 
13: EX-101.PRE  XBRL Presentations -- idt-20200731_pre               XML   1.15M 
 9: EX-101.SCH  XBRL Schema -- idt-20200731                          XSD    330K 
127: JSON        XBRL Instance as JSON Data -- MetaLinks              536±   778K  
128: ZIP         XBRL Zipped Folder -- 0001213900-20-031279-xbrl      Zip    311K  


‘EX-101.DEF’   —   XBRL Definitions — idt-20200731_def


This Exhibit is an XBRL XML File.


                                                                                                                                                                                
<?xml version="1.0" encoding="windows-1252"?>
<!-- Generated by CompSci Transform (tm) - http://www.compsciresources.com -->
<!-- Created: Wed Oct 14 12:12:57 EDT 2020 -->
<linkbase xmlns="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:xbrldt="http://xbrl.org/2005/xbrldt">
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ConsolidatedBalanceSheet" roleURI="http://www.www.idt.net/role/ConsolidatedBalanceSheet"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ConsolidatedBalanceSheet_Parentheticals" roleURI="http://www.www.idt.net/role/ConsolidatedBalanceSheet_Parentheticals"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ConsolidatedIncomeStatement" roleURI="http://www.www.idt.net/role/ConsolidatedIncomeStatement"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ConsolidatedBalanceSheet0" roleURI="http://www.www.idt.net/role/ConsolidatedBalanceSheet0"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ShareholdersEquityType2or3" roleURI="http://www.www.idt.net/role/ShareholdersEquityType2or3"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ConsolidatedCashFlow" roleURI="http://www.www.idt.net/role/ConsolidatedCashFlow"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_DescriptionofBusinessandSummaryofSignificantAccountingPolicies" roleURI="http://www.www.idt.net/role/DescriptionofBusinessandSummaryofSignificantAccountingPolicies"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_RevenueRecognition" roleURI="http://www.www.idt.net/role/RevenueRecognition"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_Leases" roleURI="http://www.www.idt.net/role/Leases"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_CashCashEquivalentsandRestrictedCashandCashEquivalents" roleURI="http://www.www.idt.net/role/CashCashEquivalentsandRestrictedCashandCashEquivalents"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_Acquisitions" roleURI="http://www.www.idt.net/role/Acquisitions"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_DebtSecurities" roleURI="http://www.www.idt.net/role/DebtSecurities"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_EquityInvestments" roleURI="http://www.www.idt.net/role/EquityInvestments"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_FairValueMeasurements" roleURI="http://www.www.idt.net/role/FairValueMeasurements"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_PropertyPlantandEquipment" roleURI="http://www.www.idt.net/role/PropertyPlantandEquipment"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_Goodwill" roleURI="http://www.www.idt.net/role/Goodwill"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_OtherIntangibleAssets" roleURI="http://www.www.idt.net/role/OtherIntangibleAssets"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_OtherOperatingExpenseNet" roleURI="http://www.www.idt.net/role/OtherOperatingExpenseNet"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_NotePayableandRevolvingCreditLoanPayable" roleURI="http://www.www.idt.net/role/NotePayableandRevolvingCreditLoanPayable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_AccruedExpenses" roleURI="http://www.www.idt.net/role/AccruedExpenses"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_OtherExpenseIncomeNet" roleURI="http://www.www.idt.net/role/OtherExpenseIncomeNet"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_IncomeTaxes" roleURI="http://www.www.idt.net/role/IncomeTaxes"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_Equity" roleURI="http://www.www.idt.net/role/Equity"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_StockBasedCompensation" roleURI="http://www.www.idt.net/role/StockBasedCompensation"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_AccumulatedOtherComprehensiveLoss" roleURI="http://www.www.idt.net/role/AccumulatedOtherComprehensiveLoss"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_CommitmentsandContingencies" roleURI="http://www.www.idt.net/role/CommitmentsandContingencies"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_RelatedPartyTransactions" roleURI="http://www.www.idt.net/role/RelatedPartyTransactions"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_DefinedContributionPlans" roleURI="http://www.www.idt.net/role/DefinedContributionPlans"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_BusinessSegmentInformation" roleURI="http://www.www.idt.net/role/BusinessSegmentInformation"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_AccountingPoliciesByPolicy" roleURI="http://www.www.idt.net/role/AccountingPoliciesByPolicy"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesTables" roleURI="http://www.www.idt.net/role/DescriptionofBusinessandSummaryofSignificantAccountingPoliciesTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_RevenueRecognitionTables" roleURI="http://www.www.idt.net/role/RevenueRecognitionTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_LeasesTables" roleURI="http://www.www.idt.net/role/LeasesTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_CashCashEquivalentsandRestrictedCashandCashEquivalentsTables" roleURI="http://www.www.idt.net/role/CashCashEquivalentsandRestrictedCashandCashEquivalentsTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_AcquisitionsTables" roleURI="http://www.www.idt.net/role/AcquisitionsTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_DebtSecuritiesTables" roleURI="http://www.www.idt.net/role/DebtSecuritiesTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_EquityInvestmentsTables" roleURI="http://www.www.idt.net/role/EquityInvestmentsTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_FairValueMeasurementsTables" roleURI="http://www.www.idt.net/role/FairValueMeasurementsTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_PropertyPlantandEquipmentTables" roleURI="http://www.www.idt.net/role/PropertyPlantandEquipmentTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_GoodwillTables" roleURI="http://www.www.idt.net/role/GoodwillTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_OtherIntangibleAssetsTables" roleURI="http://www.www.idt.net/role/OtherIntangibleAssetsTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_OtherOperatingExpenseNetTables" roleURI="http://www.www.idt.net/role/OtherOperatingExpenseNetTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_AccruedExpensesTables" roleURI="http://www.www.idt.net/role/AccruedExpensesTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_OtherExpenseIncomeNetTables" roleURI="http://www.www.idt.net/role/OtherExpenseIncomeNetTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_IncomeTaxesTables" roleURI="http://www.www.idt.net/role/IncomeTaxesTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_StockBasedCompensationTables" roleURI="http://www.www.idt.net/role/StockBasedCompensationTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_AccumulatedOtherComprehensiveLossTables" roleURI="http://www.www.idt.net/role/AccumulatedOtherComprehensiveLossTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_BusinessSegmentInformationTables" roleURI="http://www.www.idt.net/role/BusinessSegmentInformationTables"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofweightedaveragenumberofsharesusedinthecalculationofbasicanddilutedearningspershareTable" roleURI="http://www.www.idt.net/role/ScheduleofweightedaveragenumberofsharesusedinthecalculationofbasicanddilutedearningspershareTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofoutstandingstockoptionsexcludedfromthecalculationofdilutedearningspershareTable" roleURI="http://www.www.idt.net/role/ScheduleofoutstandingstockoptionsexcludedfromthecalculationofdilutedearningspershareTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofchangeintheallowancefordoubtfulaccountsTable" roleURI="http://www.www.idt.net/role/ScheduleofchangeintheallowancefordoubtfulaccountsTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofrevenuesdisaggregatedbybusinesssegmentandserviceofferedtocustomersTable" roleURI="http://www.www.idt.net/role/ScheduleofrevenuesdisaggregatedbybusinesssegmentandserviceofferedtocustomersTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofrevenuesdisaggregatedbygeographicregionTable" roleURI="http://www.www.idt.net/role/ScheduleofrevenuesdisaggregatedbygeographicregionTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofdeferredcustomercontractacquisitioncostsTable" roleURI="http://www.www.idt.net/role/ScheduleofdeferredcustomercontractacquisitioncostsTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofsupplementaldisclosuresrelatedtotheCompanysoperatingleasesTable" roleURI="http://www.www.idt.net/role/ScheduleofsupplementaldisclosuresrelatedtotheCompanysoperatingleasesTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofsupplementaldisclosuresrelatedweightedaverageoperatingleasesTable" roleURI="http://www.www.idt.net/role/ScheduleofsupplementaldisclosuresrelatedweightedaverageoperatingleasesTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofaggregateoperatingleaseliabilityTable" roleURI="http://www.www.idt.net/role/ScheduleofaggregateoperatingleaseliabilityTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleoffutureminimummaturitiesofoperatingleaseliabilitiesTable" roleURI="http://www.www.idt.net/role/ScheduleoffutureminimummaturitiesofoperatingleaseliabilitiesTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleoffutureminimumpaymentsforoperatingleasesTable" roleURI="http://www.www.idt.net/role/ScheduleoffutureminimumpaymentsforoperatingleasesTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofcashcashequivalentsandrestrictedcashandcashequivalentsTable" roleURI="http://www.www.idt.net/role/ScheduleofcashcashequivalentsandrestrictedcashandcashequivalentsTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofacquisitiondatefairvalueofconsiderationTable" roleURI="http://www.www.idt.net/role/ScheduleofacquisitiondatefairvalueofconsiderationTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofimpactoftheacquisitionspurchasepriceallocationsonconsolidatedbalancesheetTable" roleURI="http://www.www.idt.net/role/ScheduleofimpactoftheacquisitionspurchasepriceallocationsonconsolidatedbalancesheetTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofconsolidatedbalancesheetandacquisitiondatefairvalueoftotalconsiderationtransferredTable" roleURI="http://www.www.idt.net/role/ScheduleofconsolidatedbalancesheetandacquisitiondatefairvalueoftotalconsiderationtransferredTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofavailableforsalesecuritiesTable" roleURI="http://www.www.idt.net/role/ScheduleofavailableforsalesecuritiesTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofcontractualmaturitiesofavailableforsaledebtsecuritiesTable" roleURI="http://www.www.idt.net/role/ScheduleofcontractualmaturitiesofavailableforsaledebtsecuritiesTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofavailableforsalesecuritiesunrealizedlosspositionTable" roleURI="http://www.www.idt.net/role/ScheduleofavailableforsalesecuritiesunrealizedlosspositionTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofequityinvestmentsTable" roleURI="http://www.www.idt.net/role/ScheduleofequityinvestmentsTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofequityinvestmentsTable_Parentheticals" roleURI="http://www.www.idt.net/role/ScheduleofequityinvestmentsTable_Parentheticals"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofcarryingvalueofequityinvestmentsTable" roleURI="http://www.www.idt.net/role/ScheduleofcarryingvalueofequityinvestmentsTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofunrealizedgainsandlossesforallequityinvestmentsTable" roleURI="http://www.www.idt.net/role/ScheduleofunrealizedgainsandlossesforallequityinvestmentsTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofbalanceofassetsmeasuredatfairvalueonarecurringbasisTable" roleURI="http://www.www.idt.net/role/ScheduleofbalanceofassetsmeasuredatfairvalueonarecurringbasisTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofassetsmeasuredatfairvalueonarecurringbasisusingsignificantunobservableinputsLevel3Table" roleURI="http://www.www.idt.net/role/ScheduleofassetsmeasuredatfairvalueonarecurringbasisusingsignificantunobservableinputsLevel3Table"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofliabilitiesmeasuredatfairvalueonarecurringbasisusingsignificantunobservableinputsLevel3Table" roleURI="http://www.www.idt.net/role/ScheduleofliabilitiesmeasuredatfairvalueonarecurringbasisusingsignificantunobservableinputsLevel3Table"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofpropertyplantandequipmentTable" roleURI="http://www.www.idt.net/role/ScheduleofpropertyplantandequipmentTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofchangeincarryingamountofgoodwillbyoperatingsegmentTable" roleURI="http://www.www.idt.net/role/ScheduleofchangeincarryingamountofgoodwillbyoperatingsegmentTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofpresentsinformationontheCompanysamortizedintangibleassetsTable" roleURI="http://www.www.idt.net/role/ScheduleofpresentsinformationontheCompanysamortizedintangibleassetsTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofotheroperatingexpensenetTable" roleURI="http://www.www.idt.net/role/ScheduleofotheroperatingexpensenetTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofaccruedexpensesTable" roleURI="http://www.www.idt.net/role/ScheduleofaccruedexpensesTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofotherexpenseincomenetTable" roleURI="http://www.www.idt.net/role/ScheduleofotherexpenseincomenetTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofincomebeforeincometaxesTable" roleURI="http://www.www.idt.net/role/ScheduleofincomebeforeincometaxesTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofdeferredincometaxassetsTable" roleURI="http://www.www.idt.net/role/ScheduleofdeferredincometaxassetsTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofbenefitfromprovisionforincometaxesTable" roleURI="http://www.www.idt.net/role/ScheduleofbenefitfromprovisionforincometaxesTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofUSfederalstatutoryincometaxrateandincometaxesprovidedTable" roleURI="http://www.www.idt.net/role/ScheduleofUSfederalstatutoryincometaxrateandincometaxesprovidedTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofchangeinthevaluationallowanceTable" roleURI="http://www.www.idt.net/role/ScheduleofchangeinthevaluationallowanceTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofstockoptionactivityTable" roleURI="http://www.www.idt.net/role/ScheduleofstockoptionactivityTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofgrantsofrestrictedsharesofClassBcommonstockTable" roleURI="http://www.www.idt.net/role/ScheduleofgrantsofrestrictedsharesofClassBcommonstockTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofgrantsofrestrictedsharesTable" roleURI="http://www.www.idt.net/role/ScheduleofgrantsofrestrictedsharesTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofaccumulatedbalancesforeachclassificationofothercomprehensivelossTable" roleURI="http://www.www.idt.net/role/ScheduleofaccumulatedbalancesforeachclassificationofothercomprehensivelossTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofoperatingresultsofbusinesssegmentsTable" roleURI="http://www.www.idt.net/role/ScheduleofoperatingresultsofbusinesssegmentsTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_ScheduleofnetlonglivedassetsandtotalassetsbygeographicareasTable" roleURI="http://www.www.idt.net/role/ScheduleofnetlonglivedassetsandtotalassetsbygeographicareasTable"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetails" roleURI="http://www.www.idt.net/role/DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_RevenueRecognitionDetails" roleURI="http://www.www.idt.net/role/RevenueRecognitionDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_LeasesDetails" roleURI="http://www.www.idt.net/role/LeasesDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_CashCashEquivalentsandRestrictedCashandCashEquivalentsDetails" roleURI="http://www.www.idt.net/role/CashCashEquivalentsandRestrictedCashandCashEquivalentsDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_AcquisitionsDetails" roleURI="http://www.www.idt.net/role/AcquisitionsDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_DebtSecuritiesDetails" roleURI="http://www.www.idt.net/role/DebtSecuritiesDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_EquityInvestmentsDetails" roleURI="http://www.www.idt.net/role/EquityInvestmentsDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_FairValueMeasurementsDetails" roleURI="http://www.www.idt.net/role/FairValueMeasurementsDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_PropertyPlantandEquipmentDetails" roleURI="http://www.www.idt.net/role/PropertyPlantandEquipmentDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_OtherIntangibleAssetsDetails" roleURI="http://www.www.idt.net/role/OtherIntangibleAssetsDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_OtherOperatingExpenseNetDetails" roleURI="http://www.www.idt.net/role/OtherOperatingExpenseNetDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_NotePayableandRevolvingCreditLoanPayableDetails" roleURI="http://www.www.idt.net/role/NotePayableandRevolvingCreditLoanPayableDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_IncomeTaxesDetails" roleURI="http://www.www.idt.net/role/IncomeTaxesDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_EquityDetails" roleURI="http://www.www.idt.net/role/EquityDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_StockBasedCompensationDetails" roleURI="http://www.www.idt.net/role/StockBasedCompensationDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_CommitmentsandContingenciesDetails" roleURI="http://www.www.idt.net/role/CommitmentsandContingenciesDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_RelatedPartyTransactionsDetails" roleURI="http://www.www.idt.net/role/RelatedPartyTransactionsDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_DefinedContributionPlansDetails" roleURI="http://www.www.idt.net/role/DefinedContributionPlansDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#idt_r_BusinessSegmentInformationDetails" roleURI="http://www.www.idt.net/role/BusinessSegmentInformationDetails"/>
<roleRef xlink:type="simple" xlink:href="idt-20200731.xsd#DocumentAndEntityInformation" roleURI="http://www.www.idt.net/role/DocumentAndEntityInformation"/>
<arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default"/>
<arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain"/>
<arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension"/>
<arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member"/>
<arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" arcroleURI="http://xbrl.org/int/dim/arcrole/all"/>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ConsolidatedBalanceSheet">
<loc xlink:type="locator" xlink:label="us-gaap_StatementLineItems" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementLineItems"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementTable" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementClassOfStockAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementClassOfStockAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommonClassAMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonClassAMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonClassAMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommonClassBMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonClassBMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonClassBMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AssetsAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AssetsAbstract" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AssetsCurrentAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsCurrentAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_AssetsCurrentAbstract" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DebtSecuritiesCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtSecuritiesCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="us-gaap_DebtSecuritiesCurrent" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_EquityInvestmentsCurrent" xlink:href="idt-20200731.xsd#idt_EquityInvestmentsCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="idt_EquityInvestmentsCurrent" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ReceivablesNetCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReceivablesNetCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="us-gaap_ReceivablesNetCurrent" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PrepaidExpenseCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PrepaidExpenseCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="us-gaap_PrepaidExpenseCurrent" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherAssetsCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetsCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="us-gaap_OtherAssetsCurrent" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AssetsCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="us-gaap_AssetsCurrent" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentNet" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_PropertyPlantAndEquipmentNet" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_Goodwill" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_Goodwill" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherIntangibleAssetsNet" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherIntangibleAssetsNet"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_OtherIntangibleAssetsNet" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LongTermInvestments" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermInvestments"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_LongTermInvestments" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_OperatingLeaseRightOfUseAsset" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredIncomeTaxAssetsNet" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_DeferredIncomeTaxAssetsNet" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherAssetsNoncurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetsNoncurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_OtherAssetsNoncurrent" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_Assets" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Assets"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_Assets" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_LiabilitiesAndStockholdersEquityAbstract" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LiabilitiesCurrentAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_LiabilitiesCurrentAbstract" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AccountsPayableCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountsPayableCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_AccountsPayableCurrent" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AccruedLiabilitiesCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_AccruedLiabilitiesCurrent" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredRevenueCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredRevenueCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_DeferredRevenueCurrent" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DepositLiabilityCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DepositLiabilityCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_DepositLiabilityCurrent" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherLiabilitiesCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherLiabilitiesCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_OtherLiabilitiesCurrent" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LiabilitiesCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_LiabilitiesCurrent" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_OperatingLeaseLiabilityNoncurrent" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherLiabilitiesNoncurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_OtherLiabilitiesNoncurrent" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_Liabilities" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Liabilities"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_Liabilities" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommitmentsAndContingencies" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommitmentsAndContingencies"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_CommitmentsAndContingencies" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EquityAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_EquityAbstract" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StockholdersEquityAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityAbstract" xlink:to="us-gaap_StockholdersEquityAbstract" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PreferredStockValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_PreferredStockValue" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommonStockValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_CommonStockValue" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AdditionalPaidInCapital" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdditionalPaidInCapital"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityAbstract" xlink:to="us-gaap_AdditionalPaidInCapital" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_TreasuryStockValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityAbstract" xlink:to="us-gaap_TreasuryStockValue" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityAbstract" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityAbstract" xlink:to="us-gaap_RetainedEarningsAccumulatedDeficit" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StockholdersEquity" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquity"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityAbstract" xlink:to="us-gaap_StockholdersEquity" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_MinorityInterest" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MinorityInterest"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_MinorityInterest" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_LiabilitiesAndStockholdersEquity" order="3" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ConsolidatedBalanceSheet_Parentheticals">
<loc xlink:type="locator" xlink:label="us-gaap_StatementLineItems" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementLineItems"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementTable" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementClassOfStockAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementClassOfStockAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommonClassAMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonClassAMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonClassAMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommonClassBMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonClassBMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonClassBMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockParOrStatedValuePerShare"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockParOrStatedValuePerShare" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PreferredStockSharesAuthorized" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockSharesAuthorized"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockSharesAuthorized" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PreferredStockSharesIssued" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockSharesIssued"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockSharesIssued" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockParOrStatedValuePerShare" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommonStockSharesAuthorized" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesAuthorized"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockSharesAuthorized" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommonStockSharesIssued" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesIssued"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockSharesIssued" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommonStockSharesOutstanding" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockSharesOutstanding" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_TreasuryStockShares" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockShares"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_TreasuryStockShares" order="9" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ConsolidatedIncomeStatement">
<loc xlink:type="locator" xlink:label="us-gaap_IncomeStatementAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_Revenues" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Revenues"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementAbstract" xlink:to="us-gaap_Revenues" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingExpensesAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingExpensesAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementAbstract" xlink:to="us-gaap_OperatingExpensesAbstract" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingCostsAndExpenses" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingCostsAndExpenses"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_OperatingCostsAndExpenses" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_SellingGeneralAndAdministrativeExpense" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DepreciationAndAmortization" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DepreciationAndAmortization"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_DepreciationAndAmortization" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SeveranceCosts1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SeveranceCosts1"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_SeveranceCosts1" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingExpenses" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingExpenses"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementAbstract" xlink:to="us-gaap_OperatingExpenses" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherOperatingIncomeExpenseNet" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherOperatingIncomeExpenseNet"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_OtherOperatingIncomeExpenseNet" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingIncomeLoss" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingIncomeLoss"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_OperatingIncomeLoss" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_InterestIncomeExpenseNet" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestIncomeExpenseNet"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingIncomeLoss" xlink:to="us-gaap_InterestIncomeExpenseNet" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_NonoperatingIncomeExpense" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NonoperatingIncomeExpense"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingIncomeLoss" xlink:to="us-gaap_NonoperatingIncomeExpense" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncomeTaxExpenseBenefit" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:to="us-gaap_IncomeTaxExpenseBenefit" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ProfitLoss" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfitLoss"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementAbstract" xlink:to="us-gaap_ProfitLoss" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ProfitLoss" xlink:to="us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_NetIncomeLoss" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetIncomeLoss"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementAbstract" xlink:to="us-gaap_NetIncomeLoss" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EarningsPerShareBasicAndDilutedAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetIncomeLoss" xlink:to="us-gaap_EarningsPerShareBasicAndDilutedAbstract" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EarningsPerShareBasic" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarningsPerShareBasic"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EarningsPerShareBasicAndDilutedAbstract" xlink:to="us-gaap_EarningsPerShareBasic" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EarningsPerShareDiluted" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarningsPerShareDiluted"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EarningsPerShareBasicAndDilutedAbstract" xlink:to="us-gaap_EarningsPerShareDiluted" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EarningsPerShareBasicAndDilutedAbstract" xlink:to="us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract" xlink:to="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract" xlink:to="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensation" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensation"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetIncomeLoss" xlink:to="us-gaap_ShareBasedCompensation" order="1" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ConsolidatedBalanceSheet0">
<loc xlink:type="locator" xlink:label="us-gaap_StatementOfFinancialPositionAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementOfFinancialPositionAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ProfitLoss" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfitLoss"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementOfFinancialPositionAbstract" xlink:to="us-gaap_ProfitLoss" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementOfFinancialPositionAbstract" xlink:to="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract" xlink:to="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax" xlink:to="us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementOfFinancialPositionAbstract" xlink:to="us-gaap_OtherComprehensiveIncomeLossNetOfTax" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementOfFinancialPositionAbstract" xlink:to="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:to="us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementOfFinancialPositionAbstract" xlink:to="us-gaap_ComprehensiveIncomeNetOfTax" order="4" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ShareholdersEquityType2or3">
<loc xlink:type="locator" xlink:label="us-gaap_StatementLineItems" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementLineItems"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementTable" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementEquityComponentsAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementEquityComponentsAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EquityComponentDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EquityComponentDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ClassOneCommonStockMember" xlink:href="idt-20200731.xsd#idt_ClassOneCommonStockMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="idt_ClassOneCommonStockMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ClassTwoCommonStockMember" xlink:href="idt-20200731.xsd#idt_ClassTwoCommonStockMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="idt_ClassTwoCommonStockMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AdditionalPaidInCapitalMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_AdditionalPaidInCapitalMember" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_TreasuryStockMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_TreasuryStockMember" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeMember" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RetainedEarningsMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetainedEarningsMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_RetainedEarningsMember" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_NoncontrollingInterestMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoncontrollingInterestMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_NoncontrollingInterestMember" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SharesIssued" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharesIssued"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_SharesIssued" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_AdjustmentsFromChangeInRevenueRecognition" xlink:href="idt-20200731.xsd#idt_AdjustmentsFromChangeInRevenueRecognition"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="idt_AdjustmentsFromChangeInRevenueRecognition" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_CumulativeEffectOnRetainedEarningsNetOfTax" xlink:href="idt-20200731.xsd#idt_CumulativeEffectOnRetainedEarningsNetOfTax"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="idt_CumulativeEffectOnRetainedEarningsNetOfTax" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestsAdjustedBalance1" xlink:href="idt-20200731.xsd#idt_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestsAdjustedBalance1"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="idt_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestsAdjustedBalance1" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedShareBalance1" xlink:href="idt-20200731.xsd#idt_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedShareBalance1"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="idt_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedShareBalance1" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_NoncontrollingInterestIncreaseDecreaseFromCorrection" xlink:href="idt-20200731.xsd#idt_NoncontrollingInterestIncreaseDecreaseFromCorrection"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="idt_NoncontrollingInterestIncreaseDecreaseFromCorrection" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercisedNetOfTaxBenefitExpense" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercisedNetOfTaxBenefitExpense"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercisedNetOfTaxBenefitExpense" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" order="9" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_RepurchasesOfClassBCommonStockThroughRepurchaseProgram" xlink:href="idt-20200731.xsd#idt_RepurchasesOfClassBCommonStockThroughRepurchaseProgram"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="idt_RepurchasesOfClassBCommonStockThroughRepurchaseProgram" order="10" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ProceedsFromIssuanceOrSaleOfEquity" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromIssuanceOrSaleOfEquity"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_ProceedsFromIssuanceOrSaleOfEquity" order="11" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_RepurchaseOfRestrictedStock" xlink:href="idt-20200731.xsd#idt_RepurchaseOfRestrictedStock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="idt_RepurchaseOfRestrictedStock" order="12" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_StockBasedCompensation" xlink:href="idt-20200731.xsd#idt_StockBasedCompensation"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="idt_StockBasedCompensation" order="13" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation" order="14" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_DistributionToNoncontrollingInterests" xlink:href="idt-20200731.xsd#idt_DistributionToNoncontrollingInterests"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="idt_DistributionToNoncontrollingInterests" order="15" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_OtherComprehensiveIncomeLossNetOfTax" order="16" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ProfitLoss" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfitLoss"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_ProfitLoss" order="17" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ConsolidatedCashFlow">
<loc xlink:type="locator" xlink:label="us-gaap_StatementOfCashFlowsAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementOfCashFlowsAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ProfitLoss" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfitLoss"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_ProfitLoss" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DepreciationAndAmortization" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DepreciationAndAmortization"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_DepreciationAndAmortization" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredIncomeTaxesAndTaxCredits" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredIncomeTaxesAndTaxCredits"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_DeferredIncomeTaxesAndTaxCredits" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ProvisionForDoubtfulAccounts" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProvisionForDoubtfulAccounts"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_ProvisionForDoubtfulAccounts" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensation" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensation"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_ShareBasedCompensation" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherNoncashIncomeExpense" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherNoncashIncomeExpense"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_OtherNoncashIncomeExpense" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInAccountsReceivable" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInOtherCurrentLiabilities" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInOtherCurrentLiabilities"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInOtherCurrentLiabilities" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncreaseDecreaseInContractWithCustomerLiability" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInContractWithCustomerLiability" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivities" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PaymentsToAcquireMarketableSecurities" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireMarketableSecurities"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="us-gaap_PaymentsToAcquireMarketableSecurities" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivities" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PaymentsOfCapitalDistribution" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsOfCapitalDistribution"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_PaymentsOfCapitalDistribution" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RepaymentsOfOtherDebt" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RepaymentsOfOtherDebt"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_RepaymentsOfOtherDebt" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_ProceedsFromIssuanceOfCommonStock" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ProceedsFromNotesPayable" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromNotesPayable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_ProceedsFromNotesPayable" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RepaymentsOfNotesPayable" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RepaymentsOfNotesPayable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_RepaymentsOfNotesPayable" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ProceedsFromStockOptionsExercised" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromStockOptionsExercised"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_ProceedsFromStockOptionsExercised" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ProceedsFromLinesOfCredit" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromLinesOfCredit"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_ProceedsFromLinesOfCredit" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RepaymentsOfLinesOfCredit" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RepaymentsOfLinesOfCredit"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_RepaymentsOfLinesOfCredit" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PaymentsForRepurchaseOfCommonStock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_PaymentsForRepurchaseOfCommonStock" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivities" order="9" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SupplementalCashFlowInformationAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_SupplementalCashFlowInformationAbstract" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_InterestPaidNet" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestPaidNet"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SupplementalCashFlowInformationAbstract" xlink:to="us-gaap_InterestPaidNet" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncomeTaxesPaid" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxesPaid"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SupplementalCashFlowInformationAbstract" xlink:to="us-gaap_IncomeTaxesPaid" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_NoncashOrPartNoncashAcquisitionValueOfLiabilitiesAssumed1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoncashOrPartNoncashAcquisitionValueOfLiabilitiesAssumed1"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" xlink:to="us-gaap_NoncashOrPartNoncashAcquisitionValueOfLiabilitiesAssumed1" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherSignificantNoncashTransactionValueOfConsiderationGiven1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherSignificantNoncashTransactionValueOfConsiderationGiven1"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" xlink:to="us-gaap_OtherSignificantNoncashTransactionValueOfConsiderationGiven1" order="1" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/DescriptionofBusinessandSummaryofSignificantAccountingPolicies">
<loc xlink:type="locator" xlink:label="us-gaap_AccountingPoliciesAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountingPoliciesAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SignificantAccountingPoliciesTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_SignificantAccountingPoliciesTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/RevenueRecognition">
<loc xlink:type="locator" xlink:label="us-gaap_RevenueFromContractWithCustomerAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_RevenueFromContractWithCustomerTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RevenueFromContractWithCustomerAbstract" xlink:to="us-gaap_RevenueFromContractWithCustomerTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/Leases">
<loc xlink:type="locator" xlink:label="us-gaap_DisclosureTextBlockAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisclosureTextBlockAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeasesTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeasesTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DisclosureTextBlockAbstract" xlink:to="us-gaap_LesseeOperatingLeasesTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/CashCashEquivalentsandRestrictedCashandCashEquivalents">
<loc xlink:type="locator" xlink:label="us-gaap_CashAndCashEquivalentsAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_CashAndCashEquivalentsDisclosureTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsDisclosureTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CashAndCashEquivalentsAbstract" xlink:to="us-gaap_CashAndCashEquivalentsDisclosureTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/Acquisitions">
<loc xlink:type="locator" xlink:label="idt_AcquistionsAbstract" xlink:href="idt-20200731.xsd#idt_AcquistionsAbstract"/>
<loc xlink:type="locator" xlink:label="idt_Acquistions" xlink:href="idt-20200731.xsd#idt_Acquistions"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_AcquistionsAbstract" xlink:to="idt_Acquistions" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/DebtSecurities">
<loc xlink:type="locator" xlink:label="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_InvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:to="us-gaap_InvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/EquityInvestments">
<loc xlink:type="locator" xlink:label="idt_EquityInvestmentsDisclosureAbstract" xlink:href="idt-20200731.xsd#idt_EquityInvestmentsDisclosureAbstract"/>
<loc xlink:type="locator" xlink:label="idt_EquityInvestmentsDisclosureTextBlock" xlink:href="idt-20200731.xsd#idt_EquityInvestmentsDisclosureTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityInvestmentsDisclosureAbstract" xlink:to="idt_EquityInvestmentsDisclosureTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/FairValueMeasurements">
<loc xlink:type="locator" xlink:label="us-gaap_FairValueDisclosuresAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosuresAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueDisclosuresTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosuresTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_FairValueDisclosuresTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/PropertyPlantandEquipment">
<loc xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentAbstract" xlink:to="us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/Goodwill">
<loc xlink:type="locator" xlink:label="us-gaap_DisclosureTextBlockSupplementAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisclosureTextBlockSupplementAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_GoodwillDisclosureTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillDisclosureTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DisclosureTextBlockSupplementAbstract" xlink:to="us-gaap_GoodwillDisclosureTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/OtherIntangibleAssets">
<loc xlink:type="locator" xlink:label="us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_GoodwillAndIntangibleAssetsDisclosureTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillAndIntangibleAssetsDisclosureTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract" xlink:to="us-gaap_GoodwillAndIntangibleAssetsDisclosureTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/OtherOperatingExpenseNet">
<loc xlink:type="locator" xlink:label="us-gaap_OtherIncomeAndExpensesAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherIncomeAndExpensesAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherOperatingIncomeAndExpenseTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherOperatingIncomeAndExpenseTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OtherIncomeAndExpensesAbstract" xlink:to="us-gaap_OtherOperatingIncomeAndExpenseTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/NotePayableandRevolvingCreditLoanPayable">
<loc xlink:type="locator" xlink:label="idt_NotePayableAndRevolvingCreditFacilityAbstract" xlink:href="idt-20200731.xsd#idt_NotePayableAndRevolvingCreditFacilityAbstract"/>
<loc xlink:type="locator" xlink:label="idt_NotePayableAndRevolvingCreditFacility" xlink:href="idt-20200731.xsd#idt_NotePayableAndRevolvingCreditFacility"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_NotePayableAndRevolvingCreditFacilityAbstract" xlink:to="idt_NotePayableAndRevolvingCreditFacility" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/AccruedExpenses">
<loc xlink:type="locator" xlink:label="us-gaap_PayablesAndAccrualsAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PayablesAndAccrualsAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_AccountsPayableAndAccruedLiabilitiesDisclosureTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesDisclosureTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PayablesAndAccrualsAbstract" xlink:to="us-gaap_AccountsPayableAndAccruedLiabilitiesDisclosureTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/OtherExpenseIncomeNet">
<loc xlink:type="locator" xlink:label="us-gaap_OtherIncomeAndExpensesAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherIncomeAndExpensesAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherIncomeAndOtherExpenseDisclosureTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherIncomeAndOtherExpenseDisclosureTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OtherIncomeAndExpensesAbstract" xlink:to="us-gaap_OtherIncomeAndOtherExpenseDisclosureTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/IncomeTaxes">
<loc xlink:type="locator" xlink:label="us-gaap_IncomeTaxDisclosureAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxDisclosureAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxDisclosureTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="us-gaap_IncomeTaxDisclosureTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/Equity">
<loc xlink:type="locator" xlink:label="us-gaap_StockholdersEquityNoteAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityNoteAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_StockholdersEquityNoteDisclosureTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityNoteDisclosureTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityNoteAbstract" xlink:to="us-gaap_StockholdersEquityNoteDisclosureTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/StockBasedCompensation">
<loc xlink:type="locator" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract" xlink:to="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/AccumulatedOtherComprehensiveLoss">
<loc xlink:type="locator" xlink:label="us-gaap_StockholdersEquityNoteAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityNoteAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ComprehensiveIncomeNoteTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ComprehensiveIncomeNoteTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityNoteAbstract" xlink:to="us-gaap_ComprehensiveIncomeNoteTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/CommitmentsandContingencies">
<loc xlink:type="locator" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommitmentsAndContingenciesDisclosureAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommitmentsAndContingenciesDisclosureTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:to="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/RelatedPartyTransactions">
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyTransactionsAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionsAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionsDisclosureTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionsAbstract" xlink:to="us-gaap_RelatedPartyTransactionsDisclosureTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/DefinedContributionPlans">
<loc xlink:type="locator" xlink:label="us-gaap_DisclosureTextBlockSupplementAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisclosureTextBlockSupplementAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_CompensationAndEmployeeBenefitPlansOtherThanShareBasedCompensationTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CompensationAndEmployeeBenefitPlansOtherThanShareBasedCompensationTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DisclosureTextBlockSupplementAbstract" xlink:to="us-gaap_CompensationAndEmployeeBenefitPlansOtherThanShareBasedCompensationTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/BusinessSegmentInformation">
<loc xlink:type="locator" xlink:label="us-gaap_SegmentReportingAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_SegmentReportingDisclosureTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingDisclosureTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentReportingAbstract" xlink:to="us-gaap_SegmentReportingDisclosureTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/AccountingPoliciesByPolicy">
<loc xlink:type="locator" xlink:label="us-gaap_AccountingPoliciesAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountingPoliciesAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessDescriptionAndBasisOfPresentationTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessDescriptionAndBasisOfPresentationTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_BusinessDescriptionAndBasisOfPresentationTextBlock" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ConsolidationPolicyTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConsolidationPolicyTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_ConsolidationPolicyTextBlock" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_UseOfEstimates" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UseOfEstimates"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_UseOfEstimates" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RevenueRecognitionPolicyTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueRecognitionPolicyTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_RevenueRecognitionPolicyTextBlock" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CostOfSalesPolicyTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CostOfSalesPolicyTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_CostOfSalesPolicyTextBlock" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CashAndCashEquivalentsPolicyTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsPolicyTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_CashAndCashEquivalentsPolicyTextBlock" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_SubstantiallyRestrictedCashAndCashEquivalentsPolicyTextBlock" xlink:href="idt-20200731.xsd#idt_SubstantiallyRestrictedCashAndCashEquivalentsPolicyTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="idt_SubstantiallyRestrictedCashAndCashEquivalentsPolicyTextBlock" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_MarketableSecuritiesPolicy" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MarketableSecuritiesPolicy"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_MarketableSecuritiesPolicy" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_EquityInvestmentsPolicyTextBlock" xlink:href="idt-20200731.xsd#idt_EquityInvestmentsPolicyTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="idt_EquityInvestmentsPolicyTextBlock" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentPolicyTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_PropertyPlantAndEquipmentPolicyTextBlock" order="9" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_GoodwillAndIntangibleAssetsGoodwillPolicy" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillAndIntangibleAssetsGoodwillPolicy"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_GoodwillAndIntangibleAssetsGoodwillPolicy" order="10" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AdvertisingCostsPolicyTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdvertisingCostsPolicyTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_AdvertisingCostsPolicyTextBlock" order="11" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_InternalUseSoftwarePolicy" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InternalUseSoftwarePolicy"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_InternalUseSoftwarePolicy" order="12" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_MaintenanceCostPolicyPolicyTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MaintenanceCostPolicyPolicyTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_MaintenanceCostPolicyPolicyTextBlock" order="13" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock" order="14" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncomeTaxPolicyTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxPolicyTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_IncomeTaxPolicyTextBlock" order="15" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommitmentsAndContingenciesPolicyTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommitmentsAndContingenciesPolicyTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_CommitmentsAndContingenciesPolicyTextBlock" order="16" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EarningsPerSharePolicyTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarningsPerSharePolicyTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_EarningsPerSharePolicyTextBlock" order="17" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy" order="18" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ConcentrationRiskCreditRisk" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskCreditRisk"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_ConcentrationRiskCreditRisk" order="19" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ReceivablesTradeAndOtherAccountsReceivableAllowanceForDoubtfulAccountsPolicy" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReceivablesTradeAndOtherAccountsReceivableAllowanceForDoubtfulAccountsPolicy"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_ReceivablesTradeAndOtherAccountsReceivableAllowanceForDoubtfulAccountsPolicy" order="20" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueMeasurementPolicyPolicyTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementPolicyPolicyTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_FairValueMeasurementPolicyPolicyTextBlock" order="21" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_LeasesNewAccountingPronouncementsPolicyPolicyTextBlock" xlink:href="idt-20200731.xsd#idt_LeasesNewAccountingPronouncementsPolicyPolicyTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="idt_LeasesNewAccountingPronouncementsPolicyPolicyTextBlock" order="22" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" order="23" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/DescriptionofBusinessandSummaryofSignificantAccountingPoliciesTables">
<loc xlink:type="locator" xlink:label="us-gaap_AccountingPoliciesAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountingPoliciesAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTextBlock" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ScheduleOfChangesInAllowanceForDoubtfulAccountsTableTextBlock" xlink:href="idt-20200731.xsd#idt_ScheduleOfChangesInAllowanceForDoubtfulAccountsTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="idt_ScheduleOfChangesInAllowanceForDoubtfulAccountsTableTextBlock" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/RevenueRecognitionTables">
<loc xlink:type="locator" xlink:label="us-gaap_RevenueFromContractWithCustomerAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RevenueFromContractWithCustomerAbstract" xlink:to="us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTextBlock" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RevenueFromExternalCustomersByGeographicAreasTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromExternalCustomersByGeographicAreasTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RevenueFromContractWithCustomerAbstract" xlink:to="us-gaap_RevenueFromExternalCustomersByGeographicAreasTableTextBlock" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CapitalizedContractCostTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CapitalizedContractCostTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RevenueFromContractWithCustomerAbstract" xlink:to="us-gaap_CapitalizedContractCostTableTextBlock" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/LeasesTables">
<loc xlink:type="locator" xlink:label="us-gaap_DisclosureTextBlockAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisclosureTextBlockAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_LeaseCostTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LeaseCostTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DisclosureTextBlockAbstract" xlink:to="us-gaap_LeaseCostTableTextBlock" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfWeightedAverageNumberOfSharesTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfWeightedAverageNumberOfSharesTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DisclosureTextBlockAbstract" xlink:to="us-gaap_ScheduleOfWeightedAverageNumberOfSharesTableTextBlock" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeasesOfLesseeDisclosureTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasesOfLesseeDisclosureTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DisclosureTextBlockAbstract" xlink:to="us-gaap_OperatingLeasesOfLesseeDisclosureTextBlock" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DisclosureTextBlockAbstract" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DisclosureTextBlockAbstract" xlink:to="us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock" order="4" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/CashCashEquivalentsandRestrictedCashandCashEquivalentsTables">
<loc xlink:type="locator" xlink:label="us-gaap_CashAndCashEquivalentsAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfCashAndCashEquivalentsTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfCashAndCashEquivalentsTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CashAndCashEquivalentsAbstract" xlink:to="us-gaap_ScheduleOfCashAndCashEquivalentsTableTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/AcquisitionsTables">
<loc xlink:type="locator" xlink:label="idt_AcquistionsAbstract" xlink:href="idt-20200731.xsd#idt_AcquistionsAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_AcquistionsAbstract" xlink:to="us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTextBlock" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_AcquistionsAbstract" xlink:to="us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTextBlock" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ScheduleOfBusinessAcquisitionsByBalanceSheetTableTextBlock" xlink:href="idt-20200731.xsd#idt_ScheduleOfBusinessAcquisitionsByBalanceSheetTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_AcquistionsAbstract" xlink:to="idt_ScheduleOfBusinessAcquisitionsByBalanceSheetTableTextBlock" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/DebtSecuritiesTables">
<loc xlink:type="locator" xlink:label="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_MarketableSecuritiesTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MarketableSecuritiesTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:to="us-gaap_MarketableSecuritiesTextBlock" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:to="us-gaap_AvailableForSaleSecuritiesTextBlock" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValueTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValueTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:to="us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValueTableTextBlock" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/EquityInvestmentsTables">
<loc xlink:type="locator" xlink:label="idt_EquityInvestmentsDisclosureAbstract" xlink:href="idt-20200731.xsd#idt_EquityInvestmentsDisclosureAbstract"/>
<loc xlink:type="locator" xlink:label="idt_ScheduleOfEquityInvestmentsTableTextBlock" xlink:href="idt-20200731.xsd#idt_ScheduleOfEquityInvestmentsTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityInvestmentsDisclosureAbstract" xlink:to="idt_ScheduleOfEquityInvestmentsTableTextBlock" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_TradingSecuritiesAndCertainTradingAssetsTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TradingSecuritiesAndCertainTradingAssetsTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityInvestmentsDisclosureAbstract" xlink:to="us-gaap_TradingSecuritiesAndCertainTradingAssetsTextBlock" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_UnrealizedGainLossOnInvestmentsTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnrealizedGainLossOnInvestmentsTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityInvestmentsDisclosureAbstract" xlink:to="us-gaap_UnrealizedGainLossOnInvestmentsTableTextBlock" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/FairValueMeasurementsTables">
<loc xlink:type="locator" xlink:label="us-gaap_FairValueDisclosuresAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosuresAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ScheduleOfLiabilitiesMeasuredAtFairValueOnARecurringBasisUsingSignificantUnobservableInputsTableTextBlock" xlink:href="idt-20200731.xsd#idt_ScheduleOfLiabilitiesMeasuredAtFairValueOnARecurringBasisUsingSignificantUnobservableInputsTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="idt_ScheduleOfLiabilitiesMeasuredAtFairValueOnARecurringBasisUsingSignificantUnobservableInputsTableTextBlock" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/PropertyPlantandEquipmentTables">
<loc xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentAbstract" xlink:to="us-gaap_PropertyPlantAndEquipmentTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/GoodwillTables">
<loc xlink:type="locator" xlink:label="us-gaap_DisclosureTextBlockSupplementAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisclosureTextBlockSupplementAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfIntangibleAssetsAndGoodwillTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfIntangibleAssetsAndGoodwillTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DisclosureTextBlockSupplementAbstract" xlink:to="us-gaap_ScheduleOfIntangibleAssetsAndGoodwillTableTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/OtherIntangibleAssetsTables">
<loc xlink:type="locator" xlink:label="us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract" xlink:to="us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTableTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/OtherOperatingExpenseNetTables">
<loc xlink:type="locator" xlink:label="us-gaap_OtherIncomeAndExpensesAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherIncomeAndExpensesAbstract"/>
<loc xlink:type="locator" xlink:label="idt_ScheduleOfOtherOperatingExpensesGainsNetTableTextBlock" xlink:href="idt-20200731.xsd#idt_ScheduleOfOtherOperatingExpensesGainsNetTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OtherIncomeAndExpensesAbstract" xlink:to="idt_ScheduleOfOtherOperatingExpensesGainsNetTableTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/AccruedExpensesTables">
<loc xlink:type="locator" xlink:label="us-gaap_PayablesAndAccrualsAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PayablesAndAccrualsAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfAccruedLiabilitiesTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfAccruedLiabilitiesTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PayablesAndAccrualsAbstract" xlink:to="us-gaap_ScheduleOfAccruedLiabilitiesTableTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/OtherExpenseIncomeNetTables">
<loc xlink:type="locator" xlink:label="us-gaap_OtherIncomeAndExpensesAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherIncomeAndExpensesAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfOtherNonoperatingIncomeExpenseTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfOtherNonoperatingIncomeExpenseTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OtherIncomeAndExpensesAbstract" xlink:to="us-gaap_ScheduleOfOtherNonoperatingIncomeExpenseTableTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/IncomeTaxesTables">
<loc xlink:type="locator" xlink:label="us-gaap_IncomeTaxDisclosureAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxDisclosureAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfIncomeBeforeIncomeTaxDomesticAndForeignTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfIncomeBeforeIncomeTaxDomesticAndForeignTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="us-gaap_ScheduleOfIncomeBeforeIncomeTaxDomesticAndForeignTableTextBlock" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfComponentsOfIncomeTaxExpenseBenefitTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfComponentsOfIncomeTaxExpenseBenefitTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="us-gaap_ScheduleOfComponentsOfIncomeTaxExpenseBenefitTableTextBlock" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SummaryOfValuationAllowanceTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SummaryOfValuationAllowanceTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="us-gaap_SummaryOfValuationAllowanceTextBlock" order="4" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/StockBasedCompensationTables">
<loc xlink:type="locator" xlink:label="idt_StockBasedCompensationTablesLineItems" xlink:href="idt-20200731.xsd#idt_StockBasedCompensationTablesLineItems"/>
<loc xlink:type="locator" xlink:label="idt_StockBasedCompensationTablesTable" xlink:href="idt-20200731.xsd#idt_StockBasedCompensationTablesTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_StockBasedCompensationTablesLineItems" xlink:to="idt_StockBasedCompensationTablesTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementClassOfStockAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_StockBasedCompensationTablesTable" xlink:to="us-gaap_StatementClassOfStockAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommonClassBMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonClassBMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonClassBMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfShareBasedCompensationActivityTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationActivityTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationTablesLineItems" xlink:to="us-gaap_ScheduleOfShareBasedCompensationActivityTableTextBlock" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationTablesLineItems" xlink:to="us-gaap_ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/AccumulatedOtherComprehensiveLossTables">
<loc xlink:type="locator" xlink:label="us-gaap_StockholdersEquityNoteAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityNoteAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityNoteAbstract" xlink:to="us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/BusinessSegmentInformationTables">
<loc xlink:type="locator" xlink:label="us-gaap_SegmentReportingAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentReportingAbstract" xlink:to="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTextBlock" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LongLivedAssetsByGeographicAreasTableTextBlock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongLivedAssetsByGeographicAreasTableTextBlock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentReportingAbstract" xlink:to="us-gaap_LongLivedAssetsByGeographicAreasTableTextBlock" order="1" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofweightedaveragenumberofsharesusedinthecalculationofbasicanddilutedearningspershareTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfWeightedAverageNumberOfSharesUsedInTheCalculationOfBasicAndDilutedEarningsPerShareAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfWeightedAverageNumberOfSharesUsedInTheCalculationOfBasicAndDilutedEarningsPerShareAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfWeightedAverageNumberOfSharesUsedInTheCalculationOfBasicAndDilutedEarningsPerShareAbstract" xlink:to="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfWeightedAverageNumberOfSharesUsedInTheCalculationOfBasicAndDilutedEarningsPerShareAbstract" xlink:to="us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncrementalCommonSharesAttributableToCallOptionsAndWarrants" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncrementalCommonSharesAttributableToCallOptionsAndWarrants"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract" xlink:to="us-gaap_IncrementalCommonSharesAttributableToCallOptionsAndWarrants" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract" xlink:to="us-gaap_IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfWeightedAverageNumberOfSharesUsedInTheCalculationOfBasicAndDilutedEarningsPerShareAbstract" xlink:to="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofoutstandingstockoptionsexcludedfromthecalculationofdilutedearningspershareTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfOutstandingStockOptionsExcludedFromTheCalculationOfDilutedEarningsPerShareAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfOutstandingStockOptionsExcludedFromTheCalculationOfDilutedEarningsPerShareAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfOutstandingStockOptionsExcludedFromTheCalculationOfDilutedEarningsPerShareAbstract" xlink:to="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofchangeintheallowancefordoubtfulaccountsTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfChangeInTheAllowanceForDoubtfulAccountsAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfChangeInTheAllowanceForDoubtfulAccountsAbstract"/>
<loc xlink:type="locator" xlink:label="idt_ReservesDeductedFromAccountsReceivableAbstract" xlink:href="idt-20200731.xsd#idt_ReservesDeductedFromAccountsReceivableAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfChangeInTheAllowanceForDoubtfulAccountsAbstract" xlink:to="idt_ReservesDeductedFromAccountsReceivableAbstract" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AccountsReceivableGrossCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountsReceivableGrossCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ReservesDeductedFromAccountsReceivableAbstract" xlink:to="us-gaap_AccountsReceivableGrossCurrent" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ProvisionForDoubtfulAccounts" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProvisionForDoubtfulAccounts"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ReservesDeductedFromAccountsReceivableAbstract" xlink:to="us-gaap_ProvisionForDoubtfulAccounts" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AllowanceForDoubtfulAccountsReceivableWriteOffs" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableWriteOffs"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ReservesDeductedFromAccountsReceivableAbstract" xlink:to="us-gaap_AllowanceForDoubtfulAccountsReceivableWriteOffs" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofrevenuesdisaggregatedbybusinesssegmentandserviceofferedtocustomersTable">
<loc xlink:type="locator" xlink:label="us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_ProductOrServiceAxis" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductOrServiceAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:to="srt_ProductOrServiceAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_ProductsAndServicesDomain" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductsAndServicesDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_ProductOrServiceAxis" xlink:to="srt_ProductsAndServicesDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_ProductsAndServicesDomain_0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductsAndServicesDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="srt_ProductOrServiceAxis" xlink:to="srt_ProductsAndServicesDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementBusinessSegmentsAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:to="us-gaap_StatementBusinessSegmentsAxis" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SegmentDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementBusinessSegmentsAxis" xlink:to="us-gaap_SegmentDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SegmentDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementBusinessSegmentsAxis" xlink:to="us-gaap_SegmentDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_TelecomAndPaymentServiceMember" xlink:href="idt-20200731.xsd#idt_TelecomAndPaymentServiceMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentDomain" xlink:to="idt_TelecomAndPaymentServiceMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_Net2PhoneMember" xlink:href="idt-20200731.xsd#idt_Net2PhoneMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentDomain" xlink:to="idt_Net2PhoneMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_BOSSRevolutionMoneyTransferMember" xlink:href="idt-20200731.xsd#idt_BOSSRevolutionMoneyTransferMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ProductsAndServicesDomain" xlink:to="idt_BOSSRevolutionMoneyTransferMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_NationalRetailSolutionsMember" xlink:href="idt-20200731.xsd#idt_NationalRetailSolutionsMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ProductsAndServicesDomain" xlink:to="idt_NationalRetailSolutionsMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_TotalTelecomAndPaymentServicesOtherMember" xlink:href="idt-20200731.xsd#idt_TotalTelecomAndPaymentServicesOtherMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ProductsAndServicesDomain" xlink:to="idt_TotalTelecomAndPaymentServicesOtherMember" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_MobileTopUpMember" xlink:href="idt-20200731.xsd#idt_MobileTopUpMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ProductsAndServicesDomain" xlink:to="idt_MobileTopUpMember" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_BossRevolutionCallingMember" xlink:href="idt-20200731.xsd#idt_BossRevolutionCallingMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ProductsAndServicesDomain" xlink:to="idt_BossRevolutionCallingMember" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_WholesaleCarrierServicesMember" xlink:href="idt-20200731.xsd#idt_WholesaleCarrierServicesMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ProductsAndServicesDomain" xlink:to="idt_WholesaleCarrierServicesMember" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_TotalTelecomAndPaymentServicesOthersMember" xlink:href="idt-20200731.xsd#idt_TotalTelecomAndPaymentServicesOthersMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ProductsAndServicesDomain" xlink:to="idt_TotalTelecomAndPaymentServicesOthersMember" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_NetTwoPhoneUnifiedCommunicationsAsServiceMember" xlink:href="idt-20200731.xsd#idt_NetTwoPhoneUnifiedCommunicationsAsServiceMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ProductsAndServicesDomain" xlink:to="idt_NetTwoPhoneUnifiedCommunicationsAsServiceMember" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_Net2PhonePlatformServicesMember" xlink:href="idt-20200731.xsd#idt_Net2PhonePlatformServicesMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ProductsAndServicesDomain" xlink:to="idt_Net2PhonePlatformServicesMember" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_GrowthAbstract" xlink:href="idt-20200731.xsd#idt_GrowthAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="idt_GrowthAbstract" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_Revenues" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Revenues"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_GrowthAbstract" xlink:to="us-gaap_Revenues" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofrevenuesdisaggregatedbygeographicregionTable">
<loc xlink:type="locator" xlink:label="idt_RevenueRecognitionDetailsScheduleofrevenuesdisaggregatedbygeographicregionLineItems" xlink:href="idt-20200731.xsd#idt_RevenueRecognitionDetailsScheduleofrevenuesdisaggregatedbygeographicregionLineItems"/>
<loc xlink:type="locator" xlink:label="idt_RevenueRecognitionDetailsScheduleofrevenuesdisaggregatedbygeographicregionTable" xlink:href="idt-20200731.xsd#idt_RevenueRecognitionDetailsScheduleofrevenuesdisaggregatedbygeographicregionTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_RevenueRecognitionDetailsScheduleofrevenuesdisaggregatedbygeographicregionLineItems" xlink:to="idt_RevenueRecognitionDetailsScheduleofrevenuesdisaggregatedbygeographicregionTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_StatementGeographicalAxis" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_StatementGeographicalAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_RevenueRecognitionDetailsScheduleofrevenuesdisaggregatedbygeographicregionTable" xlink:to="srt_StatementGeographicalAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_SegmentGeographicalDomain" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SegmentGeographicalDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_StatementGeographicalAxis" xlink:to="srt_SegmentGeographicalDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_SegmentGeographicalDomain_0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SegmentGeographicalDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="srt_StatementGeographicalAxis" xlink:to="srt_SegmentGeographicalDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementBusinessSegmentsAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_RevenueRecognitionDetailsScheduleofrevenuesdisaggregatedbygeographicregionTable" xlink:to="us-gaap_StatementBusinessSegmentsAxis" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SegmentDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementBusinessSegmentsAxis" xlink:to="us-gaap_SegmentDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SegmentDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementBusinessSegmentsAxis" xlink:to="us-gaap_SegmentDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="country_US" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_US"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_US" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="country_GB" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_GB"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_GB" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="country_NL" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_NL"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_NL" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_OtherCountriesMember" xlink:href="idt-20200731.xsd#idt_OtherCountriesMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="idt_OtherCountriesMember" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_OutsideTheUnitedStatesMember" xlink:href="idt-20200731.xsd#idt_OutsideTheUnitedStatesMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="idt_OutsideTheUnitedStatesMember" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_TelecomAndPaymentServiceMember" xlink:href="idt-20200731.xsd#idt_TelecomAndPaymentServiceMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentDomain" xlink:to="idt_TelecomAndPaymentServiceMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_Net2phoneMember" xlink:href="idt-20200731.xsd#idt_Net2phoneMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentDomain" xlink:to="idt_Net2phoneMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_Revenues" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Revenues"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_RevenueRecognitionDetailsScheduleofrevenuesdisaggregatedbygeographicregionLineItems" xlink:to="us-gaap_Revenues" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_YearEndedJuly312019Abstract" xlink:href="idt-20200731.xsd#idt_YearEndedJuly312019Abstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_RevenueRecognitionDetailsScheduleofrevenuesdisaggregatedbygeographicregionLineItems" xlink:to="idt_YearEndedJuly312019Abstract" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_OutsideTheUnitedStatesAbstract0" xlink:href="idt-20200731.xsd#idt_OutsideTheUnitedStatesAbstract0"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_YearEndedJuly312019Abstract" xlink:to="idt_OutsideTheUnitedStatesAbstract0" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_OutsideTheUnitedStatesAbstract" xlink:href="idt-20200731.xsd#idt_OutsideTheUnitedStatesAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_RevenueRecognitionDetailsScheduleofrevenuesdisaggregatedbygeographicregionLineItems" xlink:to="idt_OutsideTheUnitedStatesAbstract" order="3" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofdeferredcustomercontractacquisitioncostsTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfDeferredCustomerContractAcquisitionCostsAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfDeferredCustomerContractAcquisitionCostsAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_CapitalizedContractCostNetCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CapitalizedContractCostNetCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfDeferredCustomerContractAcquisitionCostsAbstract" xlink:to="us-gaap_CapitalizedContractCostNetCurrent" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CapitalizedContractCostNetNoncurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CapitalizedContractCostNetNoncurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfDeferredCustomerContractAcquisitionCostsAbstract" xlink:to="us-gaap_CapitalizedContractCostNetNoncurrent" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CapitalizedContractCostNet" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CapitalizedContractCostNet"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfDeferredCustomerContractAcquisitionCostsAbstract" xlink:to="us-gaap_CapitalizedContractCostNet" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofsupplementaldisclosuresrelatedtotheCompanysoperatingleasesTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfSupplementalDisclosuresRelatedToTheCompanysOperatingLeasesAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfSupplementalDisclosuresRelatedToTheCompanysOperatingLeasesAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeaseCost" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseCost"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfSupplementalDisclosuresRelatedToTheCompanysOperatingLeasesAbstract" xlink:to="us-gaap_OperatingLeaseCost" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShortTermLeaseCost" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShortTermLeaseCost"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfSupplementalDisclosuresRelatedToTheCompanysOperatingLeasesAbstract" xlink:to="us-gaap_ShortTermLeaseCost" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LeaseCost" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LeaseCost"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfSupplementalDisclosuresRelatedToTheCompanysOperatingLeasesAbstract" xlink:to="us-gaap_LeaseCost" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CashFlowOperatingActivitiesLesseeAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashFlowOperatingActivitiesLesseeAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfSupplementalDisclosuresRelatedToTheCompanysOperatingLeasesAbstract" xlink:to="us-gaap_CashFlowOperatingActivitiesLesseeAbstract" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeasePayments" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasePayments"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CashFlowOperatingActivitiesLesseeAbstract" xlink:to="us-gaap_OperatingLeasePayments" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofsupplementaldisclosuresrelatedweightedaverageoperatingleasesTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfSupplementalDisclosuresRelatedWeightedAverageOperatingLeasesAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfSupplementalDisclosuresRelatedWeightedAverageOperatingLeasesAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfSupplementalDisclosuresRelatedWeightedAverageOperatingLeasesAbstract" xlink:to="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfSupplementalDisclosuresRelatedWeightedAverageOperatingLeasesAbstract" xlink:to="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent" order="1" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofaggregateoperatingleaseliabilityTable">
<loc xlink:type="locator" xlink:label="idt_LeasesDetailsScheduleofaggregateoperatingleaseliabilityLineItems" xlink:href="idt-20200731.xsd#idt_LeasesDetailsScheduleofaggregateoperatingleaseliabilityLineItems"/>
<loc xlink:type="locator" xlink:label="idt_LeasesDetailsScheduleofaggregateoperatingleaseliabilityTable" xlink:href="idt-20200731.xsd#idt_LeasesDetailsScheduleofaggregateoperatingleaseliabilityTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_LeasesDetailsScheduleofaggregateoperatingleaseliabilityLineItems" xlink:to="idt_LeasesDetailsScheduleofaggregateoperatingleaseliabilityTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BalanceSheetLocationAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_LeasesDetailsScheduleofaggregateoperatingleaseliabilityTable" xlink:to="us-gaap_BalanceSheetLocationAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BalanceSheetLocationDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_BalanceSheetLocationAxis" xlink:to="us-gaap_BalanceSheetLocationDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BalanceSheetLocationDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_BalanceSheetLocationAxis" xlink:to="us-gaap_BalanceSheetLocationDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherCurrentLiabilitiesMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherCurrentLiabilitiesMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_BalanceSheetLocationDomain" xlink:to="us-gaap_OtherCurrentLiabilitiesMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_LeasesDetailsScheduleofaggregateoperatingleaseliabilityLineItems" xlink:to="us-gaap_OperatingLeaseLiabilityCurrent" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_LeasesDetailsScheduleofaggregateoperatingleaseliabilityLineItems" xlink:to="us-gaap_OperatingLeaseLiabilityNoncurrent" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeaseLiability" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiability"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_LeasesDetailsScheduleofaggregateoperatingleaseliabilityLineItems" xlink:to="us-gaap_OperatingLeaseLiability" order="3" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleoffutureminimummaturitiesofoperatingleaseliabilitiesTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfFutureMinimumMaturitiesOfOperatingLeaseLiabilitiesAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfFutureMinimumMaturitiesOfOperatingLeaseLiabilitiesAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextRollingTwelveMonths" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextRollingTwelveMonths"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfFutureMinimumMaturitiesOfOperatingLeaseLiabilitiesAbstract" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextRollingTwelveMonths" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearTwo" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearTwo"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfFutureMinimumMaturitiesOfOperatingLeaseLiabilitiesAbstract" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearTwo" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearThree" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearThree"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfFutureMinimumMaturitiesOfOperatingLeaseLiabilitiesAbstract" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearThree" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFour" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFour"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfFutureMinimumMaturitiesOfOperatingLeaseLiabilitiesAbstract" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFour" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFive" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFive"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfFutureMinimumMaturitiesOfOperatingLeaseLiabilitiesAbstract" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFive" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterRollingYearFive" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterRollingYearFive"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFive" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterRollingYearFive" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfFutureMinimumMaturitiesOfOperatingLeaseLiabilitiesAbstract" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfFutureMinimumMaturitiesOfOperatingLeaseLiabilitiesAbstract" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeaseLiability" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiability"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfFutureMinimumMaturitiesOfOperatingLeaseLiabilitiesAbstract" xlink:to="us-gaap_OperatingLeaseLiability" order="7" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleoffutureminimumpaymentsforoperatingleasesTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfFutureMinimumPaymentsForOperatingLeasesAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfFutureMinimumPaymentsForOperatingLeasesAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfFutureMinimumPaymentsForOperatingLeasesAbstract" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfFutureMinimumPaymentsForOperatingLeasesAbstract" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfFutureMinimumPaymentsForOperatingLeasesAbstract" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfFutureMinimumPaymentsForOperatingLeasesAbstract" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfFutureMinimumPaymentsForOperatingLeasesAbstract" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfFutureMinimumPaymentsForOperatingLeasesAbstract" xlink:to="us-gaap_OperatingLeasesFutureMinimumPaymentsDue" order="5" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofcashcashequivalentsandrestrictedcashandcashequivalentsTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfCashCashEquivalentsAndRestrictedCashAndCashEquivalentsAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfCashCashEquivalentsAndRestrictedCashAndCashEquivalentsAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfCashCashEquivalentsAndRestrictedCashAndCashEquivalentsAbstract" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfCashCashEquivalentsAndRestrictedCashAndCashEquivalentsAbstract" xlink:to="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfCashCashEquivalentsAndRestrictedCashAndCashEquivalentsAbstract" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofacquisitiondatefairvalueofconsiderationTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfAcquisitionDateFairValueOfConsiderationAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfAcquisitionDateFairValueOfConsiderationAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_PaymentsToAcquireBusinessesGross" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfAcquisitionDateFairValueOfConsiderationAbstract" xlink:to="us-gaap_PaymentsToAcquireBusinessesGross" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfAcquisitionDateFairValueOfConsiderationAbstract" xlink:to="us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationConsiderationTransferred1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent" xlink:to="us-gaap_BusinessCombinationConsiderationTransferred1" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofimpactoftheacquisitionspurchasepriceallocationsonconsolidatedbalancesheetTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfImpactOfTheAcquisitionsPurchasePriceAllocationsOnConsolidatedBalanceSheetAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfImpactOfTheAcquisitionsPurchasePriceAllocationsOnConsolidatedBalanceSheetAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfImpactOfTheAcquisitionsPurchasePriceAllocationsOnConsolidatedBalanceSheetAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfImpactOfTheAcquisitionsPurchasePriceAllocationsOnConsolidatedBalanceSheetAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfImpactOfTheAcquisitionsPurchasePriceAllocationsOnConsolidatedBalanceSheetAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_BusinessCombinationRecognizedExcessPurchasePriceGoodwill" xlink:href="idt-20200731.xsd#idt_BusinessCombinationRecognizedExcessPurchasePriceGoodwill"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfImpactOfTheAcquisitionsPurchasePriceAllocationsOnConsolidatedBalanceSheetAbstract" xlink:to="idt_BusinessCombinationRecognizedExcessPurchasePriceGoodwill" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNonCurrentNonCompeteAgreement" xlink:href="idt-20200731.xsd#idt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNonCurrentNonCompeteAgreement"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfImpactOfTheAcquisitionsPurchasePriceAllocationsOnConsolidatedBalanceSheetAbstract" xlink:to="idt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNonCurrentNonCompeteAgreement" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNonCurrentCustomerRelationships" xlink:href="idt-20200731.xsd#idt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNonCurrentCustomerRelationships"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfImpactOfTheAcquisitionsPurchasePriceAllocationsOnConsolidatedBalanceSheetAbstract" xlink:to="idt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNonCurrentCustomerRelationships" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfImpactOfTheAcquisitionsPurchasePriceAllocationsOnConsolidatedBalanceSheetAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfImpactOfTheAcquisitionsPurchasePriceAllocationsOnConsolidatedBalanceSheetAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentAssets" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentAssets"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfImpactOfTheAcquisitionsPurchasePriceAllocationsOnConsolidatedBalanceSheetAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentAssets" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfImpactOfTheAcquisitionsPurchasePriceAllocationsOnConsolidatedBalanceSheetAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable" order="9" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAccruedExpenses" xlink:href="idt-20200731.xsd#idt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAccruedExpenses"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfImpactOfTheAcquisitionsPurchasePriceAllocationsOnConsolidatedBalanceSheetAbstract" xlink:to="idt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAccruedExpenses" order="10" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfImpactOfTheAcquisitionsPurchasePriceAllocationsOnConsolidatedBalanceSheetAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther" order="11" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfImpactOfTheAcquisitionsPurchasePriceAllocationsOnConsolidatedBalanceSheetAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities" order="12" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfImpactOfTheAcquisitionsPurchasePriceAllocationsOnConsolidatedBalanceSheetAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet" order="13" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofconsolidatedbalancesheetandacquisitiondatefairvalueoftotalconsiderationtransferredTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfConsolidatedBalanceSheetAndAcquisitionDateFairValueOfTotalConsiderationTransferredAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfConsolidatedBalanceSheetAndAcquisitionDateFairValueOfTotalConsiderationTransferredAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfConsolidatedBalanceSheetAndAcquisitionDateFairValueOfTotalConsiderationTransferredAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfConsolidatedBalanceSheetAndAcquisitionDateFairValueOfTotalConsiderationTransferredAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfConsolidatedBalanceSheetAndAcquisitionDateFairValueOfTotalConsiderationTransferredAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_idt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentNonCompeteAgreement" xlink:href="idt-20200731.xsd#idt_idt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentNonCompeteAgreement"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfConsolidatedBalanceSheetAndAcquisitionDateFairValueOfTotalConsiderationTransferredAbstract" xlink:to="idt_idt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentNonCompeteAgreement" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_idt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentCustomerRelationships" xlink:href="idt-20200731.xsd#idt_idt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentCustomerRelationships"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfConsolidatedBalanceSheetAndAcquisitionDateFairValueOfTotalConsiderationTransferredAbstract" xlink:to="idt_idt_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentCustomerRelationships" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfConsolidatedBalanceSheetAndAcquisitionDateFairValueOfTotalConsiderationTransferredAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfConsolidatedBalanceSheetAndAcquisitionDateFairValueOfTotalConsiderationTransferredAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfConsolidatedBalanceSheetAndAcquisitionDateFairValueOfTotalConsiderationTransferredAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfConsolidatedBalanceSheetAndAcquisitionDateFairValueOfTotalConsiderationTransferredAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfConsolidatedBalanceSheetAndAcquisitionDateFairValueOfTotalConsiderationTransferredAbstract" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther" order="9" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationConsiderationTransferred1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfConsolidatedBalanceSheetAndAcquisitionDateFairValueOfTotalConsiderationTransferredAbstract" xlink:to="us-gaap_BusinessCombinationConsiderationTransferred1" order="10" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PaymentsToAcquireBusinessesGross" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_BusinessCombinationConsiderationTransferred1" xlink:to="us-gaap_PaymentsToAcquireBusinessesGross" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_BusinessCombinationConsiderationTransferred1" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents" order="1" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofavailableforsalesecuritiesTable">
<loc xlink:type="locator" xlink:label="us-gaap_MarketableSecuritiesLineItems" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MarketableSecuritiesLineItems"/>
<loc xlink:type="locator" xlink:label="us-gaap_MarketableSecuritiesTable" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MarketableSecuritiesTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_MarketableSecuritiesLineItems" xlink:to="us-gaap_MarketableSecuritiesTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_InformationByCategoryOfDebtSecurityAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InformationByCategoryOfDebtSecurityAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_MarketableSecuritiesTable" xlink:to="us-gaap_InformationByCategoryOfDebtSecurityAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_InformationByCategoryOfDebtSecurityAxis" xlink:to="us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_InformationByCategoryOfDebtSecurityAxis" xlink:to="us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CertificatesOfDepositMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CertificatesOfDepositMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain" xlink:to="us-gaap_CertificatesOfDepositMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_USTreasuryBillSecuritiesMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_USTreasuryBillSecuritiesMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain" xlink:to="us-gaap_USTreasuryBillSecuritiesMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_MunicipalBondsMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MunicipalBondsMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCategoriesOfInvestmentsDomain" xlink:to="us-gaap_MunicipalBondsMember" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_MarketableSecuritiesLineItems" xlink:to="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_MarketableSecuritiesLineItems" xlink:to="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_MarketableSecuritiesLineItems" xlink:to="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_MarketableSecuritiesLineItems" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtSecurities" order="4" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofcontractualmaturitiesofavailableforsaledebtsecuritiesTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfContractualMaturitiesOfAvailableForSaleDebtSecuritiesAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfContractualMaturitiesOfAvailableForSaleDebtSecuritiesAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfContractualMaturitiesOfAvailableForSaleDebtSecuritiesAbstract" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfContractualMaturitiesOfAvailableForSaleDebtSecuritiesAbstract" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfContractualMaturitiesOfAvailableForSaleDebtSecuritiesAbstract" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfContractualMaturitiesOfAvailableForSaleDebtSecuritiesAbstract" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfContractualMaturitiesOfAvailableForSaleDebtSecuritiesAbstract" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate" order="4" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofavailableforsalesecuritiesunrealizedlosspositionTable">
<loc xlink:type="locator" xlink:label="idt_DebtSecuritiesDetailsScheduleofavailableforsalesecuritiesunrealizedlosspositionLineItems" xlink:href="idt-20200731.xsd#idt_DebtSecuritiesDetailsScheduleofavailableforsalesecuritiesunrealizedlosspositionLineItems"/>
<loc xlink:type="locator" xlink:label="idt_DebtSecuritiesDetailsScheduleofavailableforsalesecuritiesunrealizedlosspositionTable" xlink:href="idt-20200731.xsd#idt_DebtSecuritiesDetailsScheduleofavailableforsalesecuritiesunrealizedlosspositionTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_DebtSecuritiesDetailsScheduleofavailableforsalesecuritiesunrealizedlosspositionLineItems" xlink:to="idt_DebtSecuritiesDetailsScheduleofavailableforsalesecuritiesunrealizedlosspositionTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FinancialInstrumentAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancialInstrumentAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_DebtSecuritiesDetailsScheduleofavailableforsalesecuritiesunrealizedlosspositionTable" xlink:to="us-gaap_FinancialInstrumentAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FinancialInstrumentAxis" xlink:to="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_FinancialInstrumentAxis" xlink:to="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_MunicipalBondsMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MunicipalBondsMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="us-gaap_MunicipalBondsMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DebtSecuritiesDetailsScheduleofavailableforsalesecuritiesunrealizedlosspositionLineItems" xlink:to="us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DebtSecuritiesDetailsScheduleofavailableforsalesecuritiesunrealizedlosspositionLineItems" xlink:to="us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_July312019Abstract0" xlink:href="idt-20200731.xsd#idt_July312019Abstract0"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DebtSecuritiesDetailsScheduleofavailableforsalesecuritiesunrealizedlosspositionLineItems" xlink:to="idt_July312019Abstract0" order="3" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofequityinvestmentsTable">
<loc xlink:type="locator" xlink:label="idt_EquityInvestmentsDetailsScheduleofequityinvestmentsLineItems" xlink:href="idt-20200731.xsd#idt_EquityInvestmentsDetailsScheduleofequityinvestmentsLineItems"/>
<loc xlink:type="locator" xlink:label="idt_EquityInvestmentsDetailsScheduleofequityinvestmentsTable" xlink:href="idt-20200731.xsd#idt_EquityInvestmentsDetailsScheduleofequityinvestmentsTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_EquityInvestmentsDetailsScheduleofequityinvestmentsLineItems" xlink:to="idt_EquityInvestmentsDetailsScheduleofequityinvestmentsTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementClassOfStockAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_EquityInvestmentsDetailsScheduleofequityinvestmentsTable" xlink:to="us-gaap_StatementClassOfStockAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_LegalEntityAxis" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_EquityInvestmentsDetailsScheduleofequityinvestmentsTable" xlink:to="dei_LegalEntityAxis" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityDomain" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="dei_LegalEntityAxis" xlink:to="dei_EntityDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityDomain_0" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="dei_LegalEntityAxis" xlink:to="dei_EntityDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherComprehensiveIncomeLocationAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_EquityInvestmentsDetailsScheduleofequityinvestmentsTable" xlink:to="us-gaap_OtherComprehensiveIncomeLocationAxis" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherComprehensiveIncomeLocationDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_OtherComprehensiveIncomeLocationAxis" xlink:to="us-gaap_OtherComprehensiveIncomeLocationDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherComprehensiveIncomeLocationDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_OtherComprehensiveIncomeLocationAxis" xlink:to="us-gaap_OtherComprehensiveIncomeLocationDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_InvestmentTypeAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentTypeAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_EquityInvestmentsDetailsScheduleofequityinvestmentsTable" xlink:to="us-gaap_InvestmentTypeAxis" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_InvestmentTypeCategorizationMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_InvestmentTypeCategorizationMember_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommonClassBMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonClassBMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonClassBMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SeriesCPreferredStockMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SeriesCPreferredStockMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_SeriesCPreferredStockMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ZedgeIncMember" xlink:href="idt-20200731.xsd#idt_ZedgeIncMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="idt_ZedgeIncMember" order="0" xbrldt:closed="true"/>
<!-- [WMV5][XcpuxYn59dz7vgYynUDuwG7r97K2jUTysl7vcz0lJt/tSeJz73kx1cLt0ZFF2SK/vxBCY0vdSrazRC6HY9rqpLEeU+fpctc2NaTu4x24EmOquxP/Ox4OC8YGgPcryxa5X6eVf+vkJh6plu9esxQ/8g/3Nb/zpwXvfHvV/P9kjIVspJsLlBvP2EItdwq1ZJy+J7ER7MlEYGpy01/gXH9Hfs7q8UiOu78EX+4erEMHCtBsK7NiBZp2s9zqLBcKW+Fl] CSR -->
<loc xlink:type="locator" xlink:label="idt_RafaelHoldingsIncMember" xlink:href="idt-20200731.xsd#idt_RafaelHoldingsIncMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="idt_RafaelHoldingsIncMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherInvestmentsMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherInvestmentsMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OtherComprehensiveIncomeLocationDomain" xlink:to="us-gaap_OtherInvestmentsMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_MutualFundMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MutualFundMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="us-gaap_MutualFundMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_HedgeFundsMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HedgeFundsMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="us-gaap_HedgeFundsMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherShortTermInvestments" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherShortTermInvestments"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityInvestmentsDetailsScheduleofequityinvestmentsLineItems" xlink:to="us-gaap_OtherShortTermInvestments" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LongTermInvestments" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermInvestments"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OtherShortTermInvestments" xlink:to="us-gaap_LongTermInvestments" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofequityinvestmentsTable_Parentheticals">
<loc xlink:type="locator" xlink:label="idt_EquityInvestmentsDetailsScheduleofequityinvestmentsParentheticalsLineItems" xlink:href="idt-20200731.xsd#idt_EquityInvestmentsDetailsScheduleofequityinvestmentsParentheticalsLineItems"/>
<loc xlink:type="locator" xlink:label="idt_EquityInvestmentsDetailsScheduleofequityinvestmentsParentheticalsTable" xlink:href="idt-20200731.xsd#idt_EquityInvestmentsDetailsScheduleofequityinvestmentsParentheticalsTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_EquityInvestmentsDetailsScheduleofequityinvestmentsParentheticalsLineItems" xlink:to="idt_EquityInvestmentsDetailsScheduleofequityinvestmentsParentheticalsTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementClassOfStockAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_EquityInvestmentsDetailsScheduleofequityinvestmentsParentheticalsTable" xlink:to="us-gaap_StatementClassOfStockAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_LegalEntityAxis" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_EquityInvestmentsDetailsScheduleofequityinvestmentsParentheticalsTable" xlink:to="dei_LegalEntityAxis" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityDomain" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="dei_LegalEntityAxis" xlink:to="dei_EntityDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityDomain_0" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="dei_LegalEntityAxis" xlink:to="dei_EntityDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommonClassBMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonClassBMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonClassBMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ZedgeIncMember" xlink:href="idt-20200731.xsd#idt_ZedgeIncMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="idt_ZedgeIncMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_RafaelHoldingsIncMember" xlink:href="idt-20200731.xsd#idt_RafaelHoldingsIncMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="idt_RafaelHoldingsIncMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_NumberOfRelatedPartySharesReceivedInConnectionWithRestrictedStock" xlink:href="idt-20200731.xsd#idt_NumberOfRelatedPartySharesReceivedInConnectionWithRestrictedStock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityInvestmentsDetailsScheduleofequityinvestmentsParentheticalsLineItems" xlink:to="idt_NumberOfRelatedPartySharesReceivedInConnectionWithRestrictedStock" order="1" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofcarryingvalueofequityinvestmentsTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfCarryingValueOfEquityInvestmentsAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfCarryingValueOfEquityInvestmentsAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_EquitySecuritiesFvNi" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquitySecuritiesFvNi"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfCarryingValueOfEquityInvestmentsAbstract" xlink:to="us-gaap_EquitySecuritiesFvNi" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_AdoptionOfChangeInAccountingForEquityInvestments" xlink:href="idt-20200731.xsd#idt_AdoptionOfChangeInAccountingForEquityInvestments"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfCarryingValueOfEquityInvestmentsAbstract" xlink:to="idt_AdoptionOfChangeInAccountingForEquityInvestments" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_EquitySecuritiesFvNiAdjusted" xlink:href="idt-20200731.xsd#idt_EquitySecuritiesFvNiAdjusted"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfCarryingValueOfEquityInvestmentsAbstract" xlink:to="idt_EquitySecuritiesFvNiAdjusted" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfCarryingValueOfEquityInvestmentsAbstract" xlink:to="us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_EquitySecuritiesWithoutReadilyDeterminableFairValueOtherUpwardPriceAdjustmentAnnualAmount" xlink:href="idt-20200731.xsd#idt_EquitySecuritiesWithoutReadilyDeterminableFairValueOtherUpwardPriceAdjustmentAnnualAmount"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfCarryingValueOfEquityInvestmentsAbstract" xlink:to="idt_EquitySecuritiesWithoutReadilyDeterminableFairValueOtherUpwardPriceAdjustmentAnnualAmount" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_EquitySecuritiesWithoutReadilyDeterminableFairValueRedemptionsAnnualAmount" xlink:href="idt-20200731.xsd#idt_EquitySecuritiesWithoutReadilyDeterminableFairValueRedemptionsAnnualAmount"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfCarryingValueOfEquityInvestmentsAbstract" xlink:to="idt_EquitySecuritiesWithoutReadilyDeterminableFairValueRedemptionsAnnualAmount" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossAnnualAmount" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossAnnualAmount"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfCarryingValueOfEquityInvestmentsAbstract" xlink:to="us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueImpairmentLossAnnualAmount" order="6" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofunrealizedgainsandlossesforallequityinvestmentsTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfUnrealizedGainsAndLossesForAllEquityInvestmentsAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfUnrealizedGainsAndLossesForAllEquityInvestmentsAbstract"/>
<loc xlink:type="locator" xlink:label="idt_EquitySecuritiesFvNiRecognizedGainLossNet" xlink:href="idt-20200731.xsd#idt_EquitySecuritiesFvNiRecognizedGainLossNet"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfUnrealizedGainsAndLossesForAllEquityInvestmentsAbstract" xlink:to="idt_EquitySecuritiesFvNiRecognizedGainLossNet" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_EquitySecuritiesFvNiRecognizedGainLossNetOnEquitySecuritiesSold" xlink:href="idt-20200731.xsd#idt_EquitySecuritiesFvNiRecognizedGainLossNetOnEquitySecuritiesSold"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfUnrealizedGainsAndLossesForAllEquityInvestmentsAbstract" xlink:to="idt_EquitySecuritiesFvNiRecognizedGainLossNetOnEquitySecuritiesSold" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_EquitySecuritiesFvNiRecognizedUnrealizedGainLossNetEquitySecuritiesHeld" xlink:href="idt-20200731.xsd#idt_EquitySecuritiesFvNiRecognizedUnrealizedGainLossNetEquitySecuritiesHeld"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfUnrealizedGainsAndLossesForAllEquityInvestmentsAbstract" xlink:to="idt_EquitySecuritiesFvNiRecognizedUnrealizedGainLossNetEquitySecuritiesHeld" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofbalanceofassetsmeasuredatfairvalueonarecurringbasisTable">
<loc xlink:type="locator" xlink:label="idt_FairValueMeasurementsDetailsScheduleofbalanceofassetsmeasuredatfairvalueonarecurringbasisLineItems" xlink:href="idt-20200731.xsd#idt_FairValueMeasurementsDetailsScheduleofbalanceofassetsmeasuredatfairvalueonarecurringbasisLineItems"/>
<loc xlink:type="locator" xlink:label="idt_FairValueMeasurementsDetailsScheduleofbalanceofassetsmeasuredatfairvalueonarecurringbasisTable" xlink:href="idt-20200731.xsd#idt_FairValueMeasurementsDetailsScheduleofbalanceofassetsmeasuredatfairvalueonarecurringbasisTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_FairValueMeasurementsDetailsScheduleofbalanceofassetsmeasuredatfairvalueonarecurringbasisLineItems" xlink:to="idt_FairValueMeasurementsDetailsScheduleofbalanceofassetsmeasuredatfairvalueonarecurringbasisTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_FairValueMeasurementsDetailsScheduleofbalanceofassetsmeasuredatfairvalueonarecurringbasisTable" xlink:to="us-gaap_FairValueByFairValueHierarchyLevelAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_FairValueMeasurementsDetailsScheduleofbalanceofassetsmeasuredatfairvalueonarecurringbasisTable" xlink:to="us-gaap_FairValueByMeasurementFrequencyAxis" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueMeasurementFrequencyDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByMeasurementFrequencyAxis" xlink:to="us-gaap_FairValueMeasurementFrequencyDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueMeasurementFrequencyDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_FairValueByMeasurementFrequencyAxis" xlink:to="us-gaap_FairValueMeasurementFrequencyDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueMeasurementsRecurringMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementFrequencyDomain" xlink:to="us-gaap_FairValueMeasurementsRecurringMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueInputsLevel1Member" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel1Member"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel1Member" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueInputsLevel2Member" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel2Member"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel2Member" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueInputsLevel3Member" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel3Member"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel3Member" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_FairValueMeasurementsDetailsScheduleofbalanceofassetsmeasuredatfairvalueonarecurringbasisLineItems" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtSecurities" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_EquityInvestmentsCurrentAsset" xlink:href="idt-20200731.xsd#idt_EquityInvestmentsCurrentAsset"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:to="idt_EquityInvestmentsCurrentAsset" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_EquityInvestmentsNoncurrentAssets" xlink:href="idt-20200731.xsd#idt_EquityInvestmentsNoncurrentAssets"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:to="idt_EquityInvestmentsNoncurrentAssets" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_InvestmentsFairValueDisclosure" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:to="us-gaap_InvestmentsFairValueDisclosure" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ContingentConsiderationIncludedInOtherNoncurrentLiabilities" xlink:href="idt-20200731.xsd#idt_ContingentConsiderationIncludedInOtherNoncurrentLiabilities"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:to="idt_ContingentConsiderationIncludedInOtherNoncurrentLiabilities" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_July312019Abstract00" xlink:href="idt-20200731.xsd#idt_July312019Abstract00"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_FairValueMeasurementsDetailsScheduleofbalanceofassetsmeasuredatfairvalueonarecurringbasisLineItems" xlink:to="idt_July312019Abstract00" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofassetsmeasuredatfairvalueonarecurringbasisusingsignificantunobservableinputsLevel3Table">
<loc xlink:type="locator" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_StatementScenarioAxis" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_StatementScenarioAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:to="srt_StatementScenarioAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_ScenarioUnspecifiedDomain" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_StatementScenarioAxis" xlink:to="srt_ScenarioUnspecifiedDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_ScenarioUnspecifiedDomain_0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="srt_StatementScenarioAxis" xlink:to="srt_ScenarioUnspecifiedDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevelThreeFromAdoptionOfAccountingChange" xlink:href="idt-20200731.xsd#idt_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevelThreeFromAdoptionOfAccountingChange"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="idt_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevelThreeFromAdoptionOfAccountingChange" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_AmountOfChangeInUnrealizedGainsOrLossesIncludedInEarningsForAssetsHeldAtEndOfPeriod" xlink:href="idt-20200731.xsd#idt_AmountOfChangeInUnrealizedGainsOrLossesIncludedInEarningsForAssetsHeldAtEndOfPeriod"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="idt_AmountOfChangeInUnrealizedGainsOrLossesIncludedInEarningsForAssetsHeldAtEndOfPeriod" order="4" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofliabilitiesmeasuredatfairvalueonarecurringbasisusingsignificantunobservableinputsLevel3Table">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfLiabilitiesMeasuredAtFairValueOnARecurringBasisUsingSignificantUnobservableInputsLevel3Abstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfLiabilitiesMeasuredAtFairValueOnARecurringBasisUsingSignificantUnobservableInputsLevel3Abstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfLiabilitiesMeasuredAtFairValueOnARecurringBasisUsingSignificantUnobservableInputsLevel3Abstract" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesTransfersIntoLevelThreeFromAcquisition" xlink:href="idt-20200731.xsd#idt_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesTransfersIntoLevelThreeFromAcquisition"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfLiabilitiesMeasuredAtFairValueOnARecurringBasisUsingSignificantUnobservableInputsLevel3Abstract" xlink:to="idt_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesTransfersIntoLevelThreeFromAcquisition" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfLiabilitiesMeasuredAtFairValueOnARecurringBasisUsingSignificantUnobservableInputsLevel3Abstract" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_AmountOfChangeInUnrealizedGainsOrLossesIncludedInEarningsForLiabilitiesHeldAtEndOfPeriod" xlink:href="idt-20200731.xsd#idt_AmountOfChangeInUnrealizedGainsOrLossesIncludedInEarningsForLiabilitiesHeldAtEndOfPeriod"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfLiabilitiesMeasuredAtFairValueOnARecurringBasisUsingSignificantUnobservableInputsLevel3Abstract" xlink:to="idt_AmountOfChangeInUnrealizedGainsOrLossesIncludedInEarningsForLiabilitiesHeldAtEndOfPeriod" order="3" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofpropertyplantandequipmentTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfPropertyPlantAndEquipmentAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfPropertyPlantAndEquipmentAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_MachineryAndEquipmentGross" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MachineryAndEquipmentGross"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfPropertyPlantAndEquipmentAbstract" xlink:to="us-gaap_MachineryAndEquipmentGross" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CapitalizedComputerSoftwareGross" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CapitalizedComputerSoftwareGross"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfPropertyPlantAndEquipmentAbstract" xlink:to="us-gaap_CapitalizedComputerSoftwareGross" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LeaseholdImprovementsGross" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LeaseholdImprovementsGross"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfPropertyPlantAndEquipmentAbstract" xlink:to="us-gaap_LeaseholdImprovementsGross" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FurnitureAndFixturesGross" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FurnitureAndFixturesGross"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfPropertyPlantAndEquipmentAbstract" xlink:to="us-gaap_FurnitureAndFixturesGross" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentGross" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfPropertyPlantAndEquipmentAbstract" xlink:to="us-gaap_PropertyPlantAndEquipmentGross" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfPropertyPlantAndEquipmentAbstract" xlink:to="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentNet" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfPropertyPlantAndEquipmentAbstract" xlink:to="us-gaap_PropertyPlantAndEquipmentNet" order="6" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofchangeincarryingamountofgoodwillbyoperatingsegmentTable">
<loc xlink:type="locator" xlink:label="idt_GoodwillDetailsScheduleofchangeincarryingamountofgoodwillbyoperatingsegmentLineItems" xlink:href="idt-20200731.xsd#idt_GoodwillDetailsScheduleofchangeincarryingamountofgoodwillbyoperatingsegmentLineItems"/>
<loc xlink:type="locator" xlink:label="idt_GoodwillDetailsScheduleofchangeincarryingamountofgoodwillbyoperatingsegmentTable" xlink:href="idt-20200731.xsd#idt_GoodwillDetailsScheduleofchangeincarryingamountofgoodwillbyoperatingsegmentTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_GoodwillDetailsScheduleofchangeincarryingamountofgoodwillbyoperatingsegmentLineItems" xlink:to="idt_GoodwillDetailsScheduleofchangeincarryingamountofgoodwillbyoperatingsegmentTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementBusinessSegmentsAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_GoodwillDetailsScheduleofchangeincarryingamountofgoodwillbyoperatingsegmentTable" xlink:to="us-gaap_StatementBusinessSegmentsAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SegmentDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementBusinessSegmentsAxis" xlink:to="us-gaap_SegmentDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SegmentDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementBusinessSegmentsAxis" xlink:to="us-gaap_SegmentDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_TelecomAndPaymentServicesMember" xlink:href="idt-20200731.xsd#idt_TelecomAndPaymentServicesMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentDomain" xlink:to="idt_TelecomAndPaymentServicesMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_Net2phoneMember" xlink:href="idt-20200731.xsd#idt_Net2phoneMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentDomain" xlink:to="idt_Net2phoneMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_Goodwill" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_GoodwillDetailsScheduleofchangeincarryingamountofgoodwillbyoperatingsegmentLineItems" xlink:to="us-gaap_Goodwill" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_GoodwillAcquiredDuringPeriod" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillAcquiredDuringPeriod"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_GoodwillDetailsScheduleofchangeincarryingamountofgoodwillbyoperatingsegmentLineItems" xlink:to="us-gaap_GoodwillAcquiredDuringPeriod" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_GoodwillForeignCurrencyTranslationGainLoss" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillForeignCurrencyTranslationGainLoss"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_GoodwillDetailsScheduleofchangeincarryingamountofgoodwillbyoperatingsegmentLineItems" xlink:to="us-gaap_GoodwillForeignCurrencyTranslationGainLoss" order="3" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofpresentsinformationontheCompanysamortizedintangibleassetsTable">
<loc xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_TradeNamesMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TradeNamesMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="us-gaap_TradeNamesMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_NoncompeteAgreementsMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoncompeteAgreementsMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="us-gaap_NoncompeteAgreementsMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CustomerRelationshipsMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CustomerRelationshipsMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="us-gaap_CustomerRelationshipsMember" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsGross" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="us-gaap_FiniteLivedIntangibleAssetsGross" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsNet" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="us-gaap_FiniteLivedIntangibleAssetsNet" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_July312019Abstract000" xlink:href="idt-20200731.xsd#idt_July312019Abstract000"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:to="idt_July312019Abstract000" order="5" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofotheroperatingexpensenetTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfOtherOperatingExpenseNetAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfOtherOperatingExpenseNetAbstract"/>
<loc xlink:type="locator" xlink:label="idt_GainLossInPeriodFromLegalFeesNetOfInsuranceClaims" xlink:href="idt-20200731.xsd#idt_GainLossInPeriodFromLegalFeesNetOfInsuranceClaims"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfOtherOperatingExpenseNetAbstract" xlink:to="idt_GainLossInPeriodFromLegalFeesNetOfInsuranceClaims" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_Net2phoneindemnificationClaim" xlink:href="idt-20200731.xsd#idt_Net2phoneindemnificationClaim"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfOtherOperatingExpenseNetAbstract" xlink:to="idt_Net2phoneindemnificationClaim" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_Net2phoneOtherNet" xlink:href="idt-20200731.xsd#idt_Net2phoneOtherNet"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfOtherOperatingExpenseNetAbstract" xlink:to="idt_Net2phoneOtherNet" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_AccrualForNonIncomeRelatedTaxes" xlink:href="idt-20200731.xsd#idt_AccrualForNonIncomeRelatedTaxes"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfOtherOperatingExpenseNetAbstract" xlink:to="idt_AccrualForNonIncomeRelatedTaxes" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_WriteoffOfAssets" xlink:href="idt-20200731.xsd#idt_WriteoffOfAssets"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfOtherOperatingExpenseNetAbstract" xlink:to="idt_WriteoffOfAssets" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_AccrualForLegalMatter" xlink:href="idt-20200731.xsd#idt_AccrualForLegalMatter"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfOtherOperatingExpenseNetAbstract" xlink:to="idt_AccrualForLegalMatter" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_SaleOfCallingCardBusinessInAsia" xlink:href="idt-20200731.xsd#idt_SaleOfCallingCardBusinessInAsia"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfOtherOperatingExpenseNetAbstract" xlink:to="idt_SaleOfCallingCardBusinessInAsia" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherOperatingIncomeExpenseNet" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherOperatingIncomeExpenseNet"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfOtherOperatingExpenseNetAbstract" xlink:to="us-gaap_OtherOperatingIncomeExpenseNet" order="7" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofaccruedexpensesTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfAccruedExpensesAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfAccruedExpensesAbstract"/>
<loc xlink:type="locator" xlink:label="idt_CarrierMinutesTermination" xlink:href="idt-20200731.xsd#idt_CarrierMinutesTermination"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfAccruedExpensesAbstract" xlink:to="idt_CarrierMinutesTermination" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_CarrierNetworkConnectivityServices" xlink:href="idt-20200731.xsd#idt_CarrierNetworkConnectivityServices"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfAccruedExpensesAbstract" xlink:to="idt_CarrierNetworkConnectivityServices" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_AccruedRegulatoryFeesCurrent" xlink:href="idt-20200731.xsd#idt_AccruedRegulatoryFeesCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfAccruedExpensesAbstract" xlink:to="idt_AccruedRegulatoryFeesCurrent" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfAccruedExpensesAbstract" xlink:to="us-gaap_EmployeeRelatedLiabilitiesCurrent" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AccruedProfessionalFeesCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccruedProfessionalFeesCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfAccruedExpensesAbstract" xlink:to="us-gaap_AccruedProfessionalFeesCurrent" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAccruedLiabilitiesCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfAccruedExpensesAbstract" xlink:to="us-gaap_OtherAccruedLiabilitiesCurrent" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AccruedLiabilitiesCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfAccruedExpensesAbstract" xlink:to="us-gaap_AccruedLiabilitiesCurrent" order="6" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofotherexpenseincomenetTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfOtherExpenseIncomeNetAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfOtherExpenseIncomeNetAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossRealized" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ForeignCurrencyTransactionGainLossRealized"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfOtherExpenseIncomeNetAbstract" xlink:to="us-gaap_ForeignCurrencyTransactionGainLossRealized" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_WriteoffOfTaxAssetsRelatedToPriorPeriods" xlink:href="idt-20200731.xsd#idt_WriteoffOfTaxAssetsRelatedToPriorPeriods"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfOtherExpenseIncomeNetAbstract" xlink:to="idt_WriteoffOfTaxAssetsRelatedToPriorPeriods" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_GainLossOnInvestments" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GainLossOnInvestments"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfOtherExpenseIncomeNetAbstract" xlink:to="us-gaap_GainLossOnInvestments" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherNonoperatingIncomeExpense" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfOtherExpenseIncomeNetAbstract" xlink:to="us-gaap_OtherNonoperatingIncomeExpense" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_NonoperatingIncomeExpense" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NonoperatingIncomeExpense"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfOtherExpenseIncomeNetAbstract" xlink:to="us-gaap_NonoperatingIncomeExpense" order="4" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofincomebeforeincometaxesTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfIncomeBeforeIncomeTaxesAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfIncomeBeforeIncomeTaxesAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfIncomeBeforeIncomeTaxesAbstract" xlink:to="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfIncomeBeforeIncomeTaxesAbstract" xlink:to="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfIncomeBeforeIncomeTaxesAbstract" xlink:to="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofdeferredincometaxassetsTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfDeferredIncomeTaxAssetsAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfDeferredIncomeTaxAssetsAbstract"/>
<loc xlink:type="locator" xlink:label="idt_DeferredIncomeTaxAssetsAbstract" xlink:href="idt-20200731.xsd#idt_DeferredIncomeTaxAssetsAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfDeferredIncomeTaxAssetsAbstract" xlink:to="idt_DeferredIncomeTaxAssetsAbstract" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DeferredIncomeTaxAssetsAbstract" xlink:to="us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DeferredIncomeTaxAssetsAbstract" xlink:to="us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DeferredIncomeTaxAssetsAbstract" xlink:to="us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsCharitableContributionCarryforwards" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsCharitableContributionCarryforwards"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DeferredIncomeTaxAssetsAbstract" xlink:to="us-gaap_DeferredTaxAssetsCharitableContributionCarryforwards" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_DeferredTaxAssetsDepreciation" xlink:href="idt-20200731.xsd#idt_DeferredTaxAssetsDepreciation"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DeferredIncomeTaxAssetsAbstract" xlink:to="idt_DeferredTaxAssetsDepreciation" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_DeferredTaxAssetsUnrealizedGains" xlink:href="idt-20200731.xsd#idt_DeferredTaxAssetsUnrealizedGains"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DeferredIncomeTaxAssetsAbstract" xlink:to="idt_DeferredTaxAssetsUnrealizedGains" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsOperatingLossCarryforwards" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsOperatingLossCarryforwards"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DeferredIncomeTaxAssetsAbstract" xlink:to="us-gaap_DeferredTaxAssetsOperatingLossCarryforwards" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsOther" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsOther"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DeferredIncomeTaxAssetsAbstract" xlink:to="us-gaap_DeferredTaxAssetsOther" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsDeferredIncome" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsDeferredIncome"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DeferredIncomeTaxAssetsAbstract" xlink:to="us-gaap_DeferredTaxAssetsDeferredIncome" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsGross" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsGross"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfDeferredIncomeTaxAssetsAbstract" xlink:to="us-gaap_DeferredTaxAssetsGross" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsValuationAllowance" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsValuationAllowance"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfDeferredIncomeTaxAssetsAbstract" xlink:to="us-gaap_DeferredTaxAssetsValuationAllowance" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsLiabilitiesNet" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsLiabilitiesNet"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfDeferredIncomeTaxAssetsAbstract" xlink:to="us-gaap_DeferredTaxAssetsLiabilitiesNet" order="3" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofbenefitfromprovisionforincometaxesTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfBenefitFromProvisionForIncomeTaxesAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfBenefitFromProvisionForIncomeTaxesAbstract"/>
<loc xlink:type="locator" xlink:label="idt_CurrentAbstract" xlink:href="idt-20200731.xsd#idt_CurrentAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfBenefitFromProvisionForIncomeTaxesAbstract" xlink:to="idt_CurrentAbstract" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CurrentFederalTaxExpenseBenefit" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CurrentFederalTaxExpenseBenefit"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_CurrentAbstract" xlink:to="us-gaap_CurrentFederalTaxExpenseBenefit" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CurrentStateAndLocalTaxExpenseBenefit" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CurrentStateAndLocalTaxExpenseBenefit"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_CurrentAbstract" xlink:to="us-gaap_CurrentStateAndLocalTaxExpenseBenefit" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CurrentForeignTaxExpenseBenefit" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CurrentForeignTaxExpenseBenefit"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_CurrentAbstract" xlink:to="us-gaap_CurrentForeignTaxExpenseBenefit" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CurrentIncomeTaxExpenseBenefit" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CurrentIncomeTaxExpenseBenefit"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_CurrentAbstract" xlink:to="us-gaap_CurrentIncomeTaxExpenseBenefit" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_DeferredAbstract" xlink:href="idt-20200731.xsd#idt_DeferredAbstract"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfBenefitFromProvisionForIncomeTaxesAbstract" xlink:to="idt_DeferredAbstract" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredFederalIncomeTaxExpenseBenefit" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredFederalIncomeTaxExpenseBenefit"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DeferredAbstract" xlink:to="us-gaap_DeferredFederalIncomeTaxExpenseBenefit" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DeferredAbstract" xlink:to="us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredForeignIncomeTaxExpenseBenefit" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredForeignIncomeTaxExpenseBenefit"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DeferredAbstract" xlink:to="us-gaap_DeferredForeignIncomeTaxExpenseBenefit" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DeferredAbstract" xlink:to="us-gaap_DeferredIncomeTaxExpenseBenefit" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncomeTaxExpenseBenefit" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfBenefitFromProvisionForIncomeTaxesAbstract" xlink:to="us-gaap_IncomeTaxExpenseBenefit" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofUSfederalstatutoryincometaxrateandincometaxesprovidedTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfUSFederalStatutoryIncomeTaxRateAndIncomeTaxesProvidedAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfUSFederalStatutoryIncomeTaxRateAndIncomeTaxesProvidedAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfUSFederalStatutoryIncomeTaxRateAndIncomeTaxesProvidedAbstract" xlink:to="us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_IncomeTaxReconciliationTransitionTaxOnForeignEarnings" xlink:href="idt-20200731.xsd#idt_IncomeTaxReconciliationTransitionTaxOnForeignEarnings"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfUSFederalStatutoryIncomeTaxRateAndIncomeTaxesProvidedAbstract" xlink:to="idt_IncomeTaxReconciliationTransitionTaxOnForeignEarnings" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfUSFederalStatutoryIncomeTaxRateAndIncomeTaxesProvidedAbstract" xlink:to="us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncomeTaxReconciliationForeignIncomeTaxRateDifferential" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationForeignIncomeTaxRateDifferential"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfUSFederalStatutoryIncomeTaxRateAndIncomeTaxesProvidedAbstract" xlink:to="us-gaap_IncomeTaxReconciliationForeignIncomeTaxRateDifferential" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncomeTaxReconciliationNondeductibleExpenseOther" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationNondeductibleExpenseOther"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfUSFederalStatutoryIncomeTaxRateAndIncomeTaxesProvidedAbstract" xlink:to="us-gaap_IncomeTaxReconciliationNondeductibleExpenseOther" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncomeTaxReconciliationOtherReconcilingItems" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationOtherReconcilingItems"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfUSFederalStatutoryIncomeTaxRateAndIncomeTaxesProvidedAbstract" xlink:to="us-gaap_IncomeTaxReconciliationOtherReconcilingItems" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncomeTaxReconciliationNondeductibleExpenseRestructuringCharges" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationNondeductibleExpenseRestructuringCharges"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfUSFederalStatutoryIncomeTaxRateAndIncomeTaxesProvidedAbstract" xlink:to="us-gaap_IncomeTaxReconciliationNondeductibleExpenseRestructuringCharges" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_IncomeTaxReconciliationTaxLawChanges" xlink:href="idt-20200731.xsd#idt_IncomeTaxReconciliationTaxLawChanges"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfUSFederalStatutoryIncomeTaxRateAndIncomeTaxesProvidedAbstract" xlink:to="idt_IncomeTaxReconciliationTaxLawChanges" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfUSFederalStatutoryIncomeTaxRateAndIncomeTaxesProvidedAbstract" xlink:to="us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_IncomeTaxExpenseBenefit" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfUSFederalStatutoryIncomeTaxRateAndIncomeTaxesProvidedAbstract" xlink:to="us-gaap_IncomeTaxExpenseBenefit" order="9" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofchangeinthevaluationallowanceTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfChangeInTheValuationAllowanceAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfChangeInTheValuationAllowanceAbstract"/>
<loc xlink:type="locator" xlink:label="idt_a2020Abstract0" xlink:href="idt-20200731.xsd#idt_a2020Abstract0"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfChangeInTheValuationAllowanceAbstract" xlink:to="idt_a2020Abstract0" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DeferredTaxAssetsValuationAllowance" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsValuationAllowance"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_a2020Abstract0" xlink:to="us-gaap_DeferredTaxAssetsValuationAllowance" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_a2020Abstract0" xlink:to="us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ValuationAllowancesAndReservesDeductions" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDeductions"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_a2020Abstract0" xlink:to="us-gaap_ValuationAllowancesAndReservesDeductions" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofstockoptionactivityTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfStockOptionActivityAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfStockOptionActivityAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfStockOptionActivityAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfStockOptionActivityAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfStockOptionActivityAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfStockOptionActivityAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfStockOptionActivityAbstract" xlink:to="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfStockOptionActivityAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfStockOptionActivityAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfStockOptionActivityAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfStockOptionActivityAbstract" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfStockOptionActivityAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" order="9" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfStockOptionActivityAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" order="10" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfStockOptionActivityAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" order="11" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfStockOptionActivityAbstract" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" order="12" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfStockOptionActivityAbstract" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" order="13" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofgrantsofrestrictedsharesofClassBcommonstockTable">
<loc xlink:type="locator" xlink:label="idt_StockBasedCompensationDetailsScheduleofgrantsofrestrictedsharesofClassBcommonstockLineItems" xlink:href="idt-20200731.xsd#idt_StockBasedCompensationDetailsScheduleofgrantsofrestrictedsharesofClassBcommonstockLineItems"/>
<loc xlink:type="locator" xlink:label="idt_StockBasedCompensationDetailsScheduleofgrantsofrestrictedsharesofClassBcommonstockTable" xlink:href="idt-20200731.xsd#idt_StockBasedCompensationDetailsScheduleofgrantsofrestrictedsharesofClassBcommonstockTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_StockBasedCompensationDetailsScheduleofgrantsofrestrictedsharesofClassBcommonstockLineItems" xlink:to="idt_StockBasedCompensationDetailsScheduleofgrantsofrestrictedsharesofClassBcommonstockTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementClassOfStockAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_StockBasedCompensationDetailsScheduleofgrantsofrestrictedsharesofClassBcommonstockTable" xlink:to="us-gaap_StatementClassOfStockAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommonClassBMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonClassBMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonClassBMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsScheduleofgrantsofrestrictedsharesofClassBcommonstockLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsScheduleofgrantsofrestrictedsharesofClassBcommonstockLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsScheduleofgrantsofrestrictedsharesofClassBcommonstockLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsScheduleofgrantsofrestrictedsharesofClassBcommonstockLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsScheduleofgrantsofrestrictedsharesofClassBcommonstockLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsScheduleofgrantsofrestrictedsharesofClassBcommonstockLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsScheduleofgrantsofrestrictedsharesofClassBcommonstockLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsScheduleofgrantsofrestrictedsharesofClassBcommonstockLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" order="8" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofgrantsofrestrictedsharesTable">
<loc xlink:type="locator" xlink:label="idt_ScheduleOfGrantsOfRestrictedSharesAbstract" xlink:href="idt-20200731.xsd#idt_ScheduleOfGrantsOfRestrictedSharesAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfGrantsOfRestrictedSharesAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfGrantsOfRestrictedSharesAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfGrantsOfRestrictedSharesAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfGrantsOfRestrictedSharesAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfGrantsOfRestrictedSharesAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfGrantsOfRestrictedSharesAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfGrantsOfRestrictedSharesAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_ScheduleOfGrantsOfRestrictedSharesAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" order="7" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofaccumulatedbalancesforeachclassificationofothercomprehensivelossTable">
<loc xlink:type="locator" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
<loc xlink:type="locator" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossTable" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeLossTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementEquityComponentsAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_AccumulatedOtherComprehensiveIncomeLossTable" xlink:to="us-gaap_StatementEquityComponentsAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EquityComponentDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EquityComponentDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AccumulatedTranslationAdjustmentMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_AccumulatedTranslationAdjustmentMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_AccumulatedOtherComprehensiveMember" xlink:href="idt-20200731.xsd#idt_AccumulatedOtherComprehensiveMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="idt_AccumulatedOtherComprehensiveMember" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_AdjustmentFromTheAdoptionOfChangeInAccountingForEquityInvestments" xlink:href="idt-20200731.xsd#idt_AdjustmentFromTheAdoptionOfChangeInAccountingForEquityInvestments"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems" xlink:to="idt_AdjustmentFromTheAdoptionOfChangeInAccountingForEquityInvestments" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_AccumulatedOtherComprehensiveIncomeLossNetOfTaxAdjusted" xlink:href="idt-20200731.xsd#idt_AccumulatedOtherComprehensiveIncomeLossNetOfTaxAdjusted"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems" xlink:to="idt_AccumulatedOtherComprehensiveIncomeLossNetOfTaxAdjusted" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems" xlink:to="us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax" order="4" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofoperatingresultsofbusinesssegmentsTable">
<loc xlink:type="locator" xlink:label="us-gaap_SegmentReportingInformationLineItems" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingInformationLineItems"/>
<loc xlink:type="locator" xlink:label="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementBusinessSegmentsAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:to="us-gaap_StatementBusinessSegmentsAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SegmentDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementBusinessSegmentsAxis" xlink:to="us-gaap_SegmentDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SegmentDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementBusinessSegmentsAxis" xlink:to="us-gaap_SegmentDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_ConsolidationItemsAxis" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:to="srt_ConsolidationItemsAxis" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_ConsolidationItemsDomain" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_ConsolidationItemsAxis" xlink:to="srt_ConsolidationItemsDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_ConsolidationItemsDomain_0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="srt_ConsolidationItemsAxis" xlink:to="srt_ConsolidationItemsDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingSegmentsMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingSegmentsMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidationItemsDomain" xlink:to="us-gaap_OperatingSegmentsMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_TelecomAndPaymentServicesMember" xlink:href="idt-20200731.xsd#idt_TelecomAndPaymentServicesMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentDomain" xlink:to="idt_TelecomAndPaymentServicesMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_Net2phoneMember" xlink:href="idt-20200731.xsd#idt_Net2phoneMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentDomain" xlink:to="idt_Net2phoneMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CorporateMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CorporateMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentDomain" xlink:to="us-gaap_CorporateMember" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_Revenues" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Revenues"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_Revenues" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingIncomeLoss" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingIncomeLoss"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_OperatingIncomeLoss" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DepreciationAndAmortization" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DepreciationAndAmortization"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_DepreciationAndAmortization" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SeveranceCosts1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SeveranceCosts1"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_SeveranceCosts1" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OtherOperatingIncomeExpenseNet" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherOperatingIncomeExpenseNet"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_OtherOperatingIncomeExpenseNet" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_YearEndedJuly312019Abstract0" xlink:href="idt-20200731.xsd#idt_YearEndedJuly312019Abstract0"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="idt_YearEndedJuly312019Abstract0" order="6" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/ScheduleofnetlonglivedassetsandtotalassetsbygeographicareasTable">
<loc xlink:type="locator" xlink:label="idt_BusinessSegmentInformationDetailsScheduleofnetlonglivedassetsandtotalassetsbygeographicareasLineItems" xlink:href="idt-20200731.xsd#idt_BusinessSegmentInformationDetailsScheduleofnetlonglivedassetsandtotalassetsbygeographicareasLineItems"/>
<loc xlink:type="locator" xlink:label="idt_BusinessSegmentInformationDetailsScheduleofnetlonglivedassetsandtotalassetsbygeographicareasTable" xlink:href="idt-20200731.xsd#idt_BusinessSegmentInformationDetailsScheduleofnetlonglivedassetsandtotalassetsbygeographicareasTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_BusinessSegmentInformationDetailsScheduleofnetlonglivedassetsandtotalassetsbygeographicareasLineItems" xlink:to="idt_BusinessSegmentInformationDetailsScheduleofnetlonglivedassetsandtotalassetsbygeographicareasTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_StatementGeographicalAxis" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_StatementGeographicalAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_BusinessSegmentInformationDetailsScheduleofnetlonglivedassetsandtotalassetsbygeographicareasTable" xlink:to="srt_StatementGeographicalAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_SegmentGeographicalDomain" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SegmentGeographicalDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_StatementGeographicalAxis" xlink:to="srt_SegmentGeographicalDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_SegmentGeographicalDomain_0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SegmentGeographicalDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="srt_StatementGeographicalAxis" xlink:to="srt_SegmentGeographicalDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="country_US" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_US"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_US" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ForeignCountrieMember" xlink:href="idt-20200731.xsd#idt_ForeignCountrieMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="idt_ForeignCountrieMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_NoncurrentAssets" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoncurrentAssets"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_BusinessSegmentInformationDetailsScheduleofnetlonglivedassetsandtotalassetsbygeographicareasLineItems" xlink:to="us-gaap_NoncurrentAssets" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_Assets" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Assets"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_BusinessSegmentInformationDetailsScheduleofnetlonglivedassetsandtotalassetsbygeographicareasLineItems" xlink:to="us-gaap_Assets" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetails">
<loc xlink:type="locator" xlink:label="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsLineItems" xlink:href="idt-20200731.xsd#idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsLineItems"/>
<loc xlink:type="locator" xlink:label="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsTable" xlink:href="idt-20200731.xsd#idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsLineItems" xlink:to="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsTable" xlink:to="us-gaap_PropertyPlantAndEquipmentByTypeAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:to="us-gaap_PropertyPlantAndEquipmentTypeDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:to="us-gaap_PropertyPlantAndEquipmentTypeDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsTable" xlink:to="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_RangeAxis" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsTable" xlink:to="srt_RangeAxis" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_RangeMember" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_RangeMember_0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsTable" xlink:to="us-gaap_ConcentrationRiskByBenchmarkAxis" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ConcentrationRiskBenchmarkDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:to="us-gaap_ConcentrationRiskBenchmarkDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ConcentrationRiskBenchmarkDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:to="us-gaap_ConcentrationRiskBenchmarkDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EquipmentMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquipmentMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:to="us-gaap_EquipmentMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ComputerSoftwareMember" xlink:href="idt-20200731.xsd#idt_ComputerSoftwareMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:to="idt_ComputerSoftwareMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FurnitureAndFixturesMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FurnitureAndFixturesMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:to="us-gaap_FurnitureAndFixturesMember" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SoftwareAndSoftwareDevelopmentCostsMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SoftwareAndSoftwareDevelopmentCostsMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:to="us-gaap_SoftwareAndSoftwareDevelopmentCostsMember" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_MinimumMember" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MinimumMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_MaximumMember" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MaximumMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CustomerListsMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CustomerListsMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="us-gaap_CustomerListsMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SalesRevenueNetMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SalesRevenueNetMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ConcentrationRiskBenchmarkDomain" xlink:to="us-gaap_SalesRevenueNetMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AccountsReceivableMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountsReceivableMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ConcentrationRiskBenchmarkDomain" xlink:to="us-gaap_AccountsReceivableMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_NumberOfReportableSegments" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NumberOfReportableSegments"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsLineItems" xlink:to="us-gaap_NumberOfReportableSegments" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_CashAndCashEquivalentsSubstantiallyRestricted" xlink:href="idt-20200731.xsd#idt_CashAndCashEquivalentsSubstantiallyRestricted"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsLineItems" xlink:to="idt_CashAndCashEquivalentsSubstantiallyRestricted" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentUsefulLife" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsLineItems" xlink:to="us-gaap_PropertyPlantAndEquipmentUsefulLife" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AdvertisingExpense" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdvertisingExpense"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsLineItems" xlink:to="us-gaap_AdvertisingExpense" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_InternalUseSoftwarePolicyDescription" xlink:href="idt-20200731.xsd#idt_InternalUseSoftwarePolicyDescription"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsLineItems" xlink:to="idt_InternalUseSoftwarePolicyDescription" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CapitalizedComputerSoftwareAmortization1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CapitalizedComputerSoftwareAmortization1"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsLineItems" xlink:to="us-gaap_CapitalizedComputerSoftwareAmortization1" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CapitalizedComputerSoftwareNet" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CapitalizedComputerSoftwareNet"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsLineItems" xlink:to="us-gaap_CapitalizedComputerSoftwareNet" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_IncomeTaxUncertaintiesPolicyLargestAmountOfBenefitGreaterThanPercentage" xlink:href="idt-20200731.xsd#idt_IncomeTaxUncertaintiesPolicyLargestAmountOfBenefitGreaterThanPercentage"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsLineItems" xlink:to="idt_IncomeTaxUncertaintiesPolicyLargestAmountOfBenefitGreaterThanPercentage" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_NumberOfCustomers" xlink:href="idt-20200731.xsd#idt_NumberOfCustomers"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsLineItems" xlink:to="idt_NumberOfCustomers" order="9" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ConcentrationRiskPercentage1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskPercentage1"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetailsLineItems" xlink:to="us-gaap_ConcentrationRiskPercentage1" order="10" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/RevenueRecognitionDetails">
<loc xlink:type="locator" xlink:label="us-gaap_RevenueFromContractWithCustomerAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_CumulativeEarningsDeficit" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CumulativeEarningsDeficit"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RevenueFromContractWithCustomerAbstract" xlink:to="us-gaap_CumulativeEarningsDeficit" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ContractWithCustomerLiabilityRevenueRecognized" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RevenueFromContractWithCustomerAbstract" xlink:to="us-gaap_ContractWithCustomerLiabilityRevenueRecognized" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CapitalizedContractCostAmortization" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CapitalizedContractCostAmortization"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RevenueFromContractWithCustomerAbstract" xlink:to="us-gaap_CapitalizedContractCostAmortization" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/LeasesDetails">
<loc xlink:type="locator" xlink:label="idt_LeasesDetailsLineItems" xlink:href="idt-20200731.xsd#idt_LeasesDetailsLineItems"/>
<loc xlink:type="locator" xlink:label="idt_LeasesDetailsTable" xlink:href="idt-20200731.xsd#idt_LeasesDetailsTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_LeasesDetailsLineItems" xlink:to="idt_LeasesDetailsTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_LeasesDetailsTable" xlink:to="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_TypeOfAdoptionMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TypeOfAdoptionMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:to="us-gaap_TypeOfAdoptionMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_TypeOfAdoptionMember_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TypeOfAdoptionMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:to="us-gaap_TypeOfAdoptionMember_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_LeasesDetailsTable" xlink:to="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_GeographicDistributionAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GeographicDistributionAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_LeasesDetailsTable" xlink:to="us-gaap_GeographicDistributionAxis" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_GeographicDistributionDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GeographicDistributionDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_GeographicDistributionAxis" xlink:to="us-gaap_GeographicDistributionDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_GeographicDistributionDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GeographicDistributionDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_GeographicDistributionAxis" xlink:to="us-gaap_GeographicDistributionDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AccountingStandardsUpdate201602Member" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountingStandardsUpdate201602Member"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TypeOfAdoptionMember" xlink:to="us-gaap_AccountingStandardsUpdate201602Member" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_RafaelHoldingsIncMember" xlink:href="idt-20200731.xsd#idt_RafaelHoldingsIncMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="idt_RafaelHoldingsIncMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_NewarkMember" xlink:href="idt-20200731.xsd#idt_NewarkMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_GeographicDistributionDomain" xlink:to="idt_NewarkMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_NewAccountingPronouncementOrChangeInAccountingPrincipleEffectOfAdoptionsQuantification" xlink:href="idt-20200731.xsd#idt_NewAccountingPronouncementOrChangeInAccountingPrincipleEffectOfAdoptionsQuantification"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_LeasesDetailsLineItems" xlink:to="idt_NewAccountingPronouncementOrChangeInAccountingPrincipleEffectOfAdoptionsQuantification" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_LeaseTermDescription" xlink:href="idt-20200731.xsd#idt_LeaseTermDescription"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_LeasesDetailsLineItems" xlink:to="idt_LeaseTermDescription" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LeaseAndRentalExpense" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LeaseAndRentalExpense"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_LeasesDetailsLineItems" xlink:to="us-gaap_LeaseAndRentalExpense" order="3" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/CashCashEquivalentsandRestrictedCashandCashEquivalentsDetails">
<loc xlink:type="locator" xlink:label="idt_CashCashEquivalentsandRestrictedCashandCashEquivalentsDetailsLineItems" xlink:href="idt-20200731.xsd#idt_CashCashEquivalentsandRestrictedCashandCashEquivalentsDetailsLineItems"/>
<loc xlink:type="locator" xlink:label="idt_CashCashEquivalentsandRestrictedCashandCashEquivalentsDetailsTable" xlink:href="idt-20200731.xsd#idt_CashCashEquivalentsandRestrictedCashandCashEquivalentsDetailsTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_CashCashEquivalentsandRestrictedCashandCashEquivalentsDetailsLineItems" xlink:to="idt_CashCashEquivalentsandRestrictedCashandCashEquivalentsDetailsTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_ProductOrServiceAxis" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductOrServiceAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_CashCashEquivalentsandRestrictedCashandCashEquivalentsDetailsTable" xlink:to="srt_ProductOrServiceAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_ProductsAndServicesDomain" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductsAndServicesDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_ProductOrServiceAxis" xlink:to="srt_ProductsAndServicesDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_ProductsAndServicesDomain_0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductsAndServicesDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="srt_ProductOrServiceAxis" xlink:to="srt_ProductsAndServicesDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_IDTFinancialServicesLimitedMember" xlink:href="idt-20200731.xsd#idt_IDTFinancialServicesLimitedMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ProductsAndServicesDomain" xlink:to="idt_IDTFinancialServicesLimitedMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_CashCashEquivalentsandRestrictedCashandCashEquivalentsDetailsLineItems" xlink:to="us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue" order="1" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/AcquisitionsDetails">
<loc xlink:type="locator" xlink:label="idt_AcquisitionsDetailsLineItems" xlink:href="idt-20200731.xsd#idt_AcquisitionsDetailsLineItems"/>
<loc xlink:type="locator" xlink:label="idt_AcquisitionsDetailsTable" xlink:href="idt-20200731.xsd#idt_AcquisitionsDetailsTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_AcquisitionsDetailsLineItems" xlink:to="idt_AcquisitionsDetailsTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessAcquisitionAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_AcquisitionsDetailsTable" xlink:to="us-gaap_BusinessAcquisitionAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessAcquisitionAcquireeDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_BusinessAcquisitionAxis" xlink:to="us-gaap_BusinessAcquisitionAcquireeDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessAcquisitionAcquireeDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_BusinessAcquisitionAxis" xlink:to="us-gaap_BusinessAcquisitionAcquireeDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_VersatureCorpMember" xlink:href="idt-20200731.xsd#idt_VersatureCorpMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_BusinessAcquisitionAcquireeDomain" xlink:to="idt_VersatureCorpMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireePercentage" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireePercentage"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_AcquisitionsDetailsLineItems" xlink:to="us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireePercentage" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_BusinessCombinationContingentConsiderationArrangementsDescription" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsDescription"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_AcquisitionsDetailsLineItems" xlink:to="us-gaap_BusinessCombinationContingentConsiderationArrangementsDescription" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PaymentsToAcquireBusinessesGross" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_AcquisitionsDetailsLineItems" xlink:to="us-gaap_PaymentsToAcquireBusinessesGross" order="3" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/DebtSecuritiesDetails">
<loc xlink:type="locator" xlink:label="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:to="us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AvailableForSaleSecuritiesGrossRealizedGains" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesGrossRealizedGains"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:to="us-gaap_AvailableForSaleSecuritiesGrossRealizedGains" order="1" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/EquityInvestmentsDetails">
<loc xlink:type="locator" xlink:label="idt_EquityInvestmentsDetailsLineItems" xlink:href="idt-20200731.xsd#idt_EquityInvestmentsDetailsLineItems"/>
<loc xlink:type="locator" xlink:label="idt_EquityInvestmentsDetailsTable" xlink:href="idt-20200731.xsd#idt_EquityInvestmentsDetailsTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_EquityInvestmentsDetailsLineItems" xlink:to="idt_EquityInvestmentsDetailsTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementClassOfStockAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_EquityInvestmentsDetailsTable" xlink:to="us-gaap_StatementClassOfStockAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementEquityComponentsAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_EquityInvestmentsDetailsTable" xlink:to="us-gaap_StatementEquityComponentsAxis" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EquityComponentDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EquityComponentDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SubsequentEventTypeAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_EquityInvestmentsDetailsTable" xlink:to="us-gaap_SubsequentEventTypeAxis" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SubsequentEventTypeDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SubsequentEventTypeDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AwardDateAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardDateAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_EquityInvestmentsDetailsTable" xlink:to="us-gaap_AwardDateAxis" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AwardDateDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardDateDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_AwardDateAxis" xlink:to="us-gaap_AwardDateDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AwardDateDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardDateDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_AwardDateAxis" xlink:to="us-gaap_AwardDateDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_VisaSeriesCConvertibleParticipatingPreferredStockMember" xlink:href="idt-20200731.xsd#idt_VisaSeriesCConvertibleParticipatingPreferredStockMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="idt_VisaSeriesCConvertibleParticipatingPreferredStockMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_VisaSeriesAConvertibleParticipatingPreferredStockMember" xlink:href="idt-20200731.xsd#idt_VisaSeriesAConvertibleParticipatingPreferredStockMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="idt_VisaSeriesAConvertibleParticipatingPreferredStockMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RetainedEarningsMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetainedEarningsMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_RetainedEarningsMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_VisaClassACommonStockMember" xlink:href="idt-20200731.xsd#idt_VisaClassACommonStockMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="idt_VisaClassACommonStockMember" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_AugustFirstTwoThousandEighteenMember" xlink:href="idt-20200731.xsd#idt_AugustFirstTwoThousandEighteenMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AwardDateDomain" xlink:to="idt_AugustFirstTwoThousandEighteenMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SubsequentEventMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SubsequentEventTypeDomain" xlink:to="us-gaap_SubsequentEventMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_NewAccountingPronouncementOrChangeInAccountingPrincipleCumulativeEffectOfChangeOnEquityOrNetAssets3" xlink:href="idt-20200731.xsd#idt_NewAccountingPronouncementOrChangeInAccountingPrincipleCumulativeEffectOfChangeOnEquityOrNetAssets3"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityInvestmentsDetailsLineItems" xlink:to="idt_NewAccountingPronouncementOrChangeInAccountingPrincipleCumulativeEffectOfChangeOnEquityOrNetAssets3" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_InvestmentOwnedBalanceShares" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentOwnedBalanceShares"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityInvestmentsDetailsLineItems" xlink:to="us-gaap_InvestmentOwnedBalanceShares" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ConvertiblePreferredStockSharesIssuedUponConversion" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConvertiblePreferredStockSharesIssuedUponConversion"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityInvestmentsDetailsLineItems" xlink:to="us-gaap_ConvertiblePreferredStockSharesIssuedUponConversion" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LongTermInvestments" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermInvestments"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityInvestmentsDetailsLineItems" xlink:to="us-gaap_LongTermInvestments" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityInvestmentsDetailsLineItems" xlink:to="us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount" order="5" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/FairValueMeasurementsDetails">
<loc xlink:type="locator" xlink:label="us-gaap_FairValueDisclosuresAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosuresAbstract"/>
<loc xlink:type="locator" xlink:label="idt_InvestmentInHedgeFunds" xlink:href="idt-20200731.xsd#idt_InvestmentInHedgeFunds"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="idt_InvestmentInHedgeFunds" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/PropertyPlantandEquipmentDetails">
<loc xlink:type="locator" xlink:label="us-gaap_PropertyPlantAndEquipmentAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_Depreciation" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Depreciation"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentAbstract" xlink:to="us-gaap_Depreciation" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/OtherIntangibleAssetsDetails">
<loc xlink:type="locator" xlink:label="us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_AmortizationOfIntangibleAssets" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract" xlink:to="us-gaap_AmortizationOfIntangibleAssets" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive" order="5" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/OtherOperatingExpenseNetDetails">
<loc xlink:type="locator" xlink:label="idt_OtherOperatingExpenseNetDetailsLineItems" xlink:href="idt-20200731.xsd#idt_OtherOperatingExpenseNetDetailsLineItems"/>
<loc xlink:type="locator" xlink:label="idt_OtherOperatingExpenseNetDetailsTable" xlink:href="idt-20200731.xsd#idt_OtherOperatingExpenseNetDetailsTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_OtherOperatingExpenseNetDetailsLineItems" xlink:to="idt_OtherOperatingExpenseNetDetailsTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_OtherOperatingExpenseNetDetailsTable" xlink:to="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_StraightPathMember" xlink:href="idt-20200731.xsd#idt_StraightPathMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="idt_StraightPathMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LegalFees" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LegalFees"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_OtherOperatingExpenseNetDetailsLineItems" xlink:to="us-gaap_LegalFees" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_UnusualOrInfrequentItemInsuranceProceeds" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnusualOrInfrequentItemInsuranceProceeds"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_OtherOperatingExpenseNetDetailsLineItems" xlink:to="us-gaap_UnusualOrInfrequentItemInsuranceProceeds" order="2" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/NotePayableandRevolvingCreditLoanPayableDetails">
<loc xlink:type="locator" xlink:label="idt_NotePayableAndRevolvingCreditFacilityAbstract" xlink:href="idt-20200731.xsd#idt_NotePayableAndRevolvingCreditFacilityAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_ProceedsFromNotesPayable" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromNotesPayable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_NotePayableAndRevolvingCreditFacilityAbstract" xlink:to="us-gaap_ProceedsFromNotesPayable" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RepaymentsOfNotesPayable" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RepaymentsOfNotesPayable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_NotePayableAndRevolvingCreditFacilityAbstract" xlink:to="us-gaap_RepaymentsOfNotesPayable" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_NotePayableAndRevolvingCreditFacilityAbstract" xlink:to="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_NotePayableAndRevolvingCreditFacilityAbstract" xlink:to="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_NotePayableAndRevolvingCreditFacilityAbstract" xlink:to="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" order="4" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/IncomeTaxesDetails">
<loc xlink:type="locator" xlink:label="idt_IncomeTaxesDetailsLineItems" xlink:href="idt-20200731.xsd#idt_IncomeTaxesDetailsLineItems"/>
<loc xlink:type="locator" xlink:label="idt_IncomeTaxesDetailsTable" xlink:href="idt-20200731.xsd#idt_IncomeTaxesDetailsTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_IncomeTaxesDetailsLineItems" xlink:to="idt_IncomeTaxesDetailsTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_ConsolidatedEntitiesAxis" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidatedEntitiesAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_IncomeTaxesDetailsTable" xlink:to="srt_ConsolidatedEntitiesAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_ConsolidatedEntitiesDomain" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidatedEntitiesDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_ConsolidatedEntitiesAxis" xlink:to="srt_ConsolidatedEntitiesDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_ConsolidatedEntitiesDomain_0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidatedEntitiesDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="srt_ConsolidatedEntitiesAxis" xlink:to="srt_ConsolidatedEntitiesDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ValuationAllowancesAndReservesTypeAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesTypeAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_IncomeTaxesDetailsTable" xlink:to="us-gaap_ValuationAllowancesAndReservesTypeAxis" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ValuationAllowancesAndReservesDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_ValuationAllowancesAndReservesTypeAxis" xlink:to="us-gaap_ValuationAllowancesAndReservesDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ValuationAllowancesAndReservesDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_ValuationAllowancesAndReservesTypeAxis" xlink:to="us-gaap_ValuationAllowancesAndReservesDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_SubsidiariesMember" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SubsidiariesMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="srt_SubsidiariesMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ValuationAllowanceUtilizedCurrentExpenseMember" xlink:href="idt-20200731.xsd#idt_ValuationAllowanceUtilizedCurrentExpenseMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ValuationAllowancesAndReservesDomain" xlink:to="idt_ValuationAllowanceUtilizedCurrentExpenseMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ValuationAllowanceUtilizedFutureExpenseMember" xlink:href="idt-20200731.xsd#idt_ValuationAllowanceUtilizedFutureExpenseMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ValuationAllowancesAndReservesDomain" xlink:to="idt_ValuationAllowanceUtilizedFutureExpenseMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_UndistributedEarningsOfForeignSubsidiaries" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UndistributedEarningsOfForeignSubsidiaries"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_IncomeTaxesDetailsLineItems" xlink:to="us-gaap_UndistributedEarningsOfForeignSubsidiaries" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OperatingLossCarryforwards" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLossCarryforwards"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_IncomeTaxesDetailsLineItems" xlink:to="us-gaap_OperatingLossCarryforwards" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ForeignNetOperatingLossCarryForwards" xlink:href="idt-20200731.xsd#idt_ForeignNetOperatingLossCarryForwards"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_IncomeTaxesDetailsLineItems" xlink:to="idt_ForeignNetOperatingLossCarryForwards" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ForeignNetOperatingLossCarryForwardsNoExpiration" xlink:href="idt-20200731.xsd#idt_ForeignNetOperatingLossCarryForwardsNoExpiration"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_IncomeTaxesDetailsLineItems" xlink:to="idt_ForeignNetOperatingLossCarryForwardsNoExpiration" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ForeignNetOperatingLossCarryForwardsExpirationTwoToTenYears" xlink:href="idt-20200731.xsd#idt_ForeignNetOperatingLossCarryForwardsExpirationTwoToTenYears"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_IncomeTaxesDetailsLineItems" xlink:to="idt_ForeignNetOperatingLossCarryForwardsExpirationTwoToTenYears" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ForeignNetOperatingLossCarryForwardsExpirationTwentyYears" xlink:href="idt-20200731.xsd#idt_ForeignNetOperatingLossCarryForwardsExpirationTwentyYears"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_IncomeTaxesDetailsLineItems" xlink:to="idt_ForeignNetOperatingLossCarryForwardsExpirationTwentyYears" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_NetOperatingLossCarryForwardsYearOfExpiration" xlink:href="idt-20200731.xsd#idt_NetOperatingLossCarryForwardsYearOfExpiration"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_IncomeTaxesDetailsLineItems" xlink:to="idt_NetOperatingLossCarryForwardsYearOfExpiration" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_TotalSubsidiaryTaxNetOperatingLossCarryForwardsAnnualLimitAmountUnderInternalRevenueCode" xlink:href="idt-20200731.xsd#idt_TotalSubsidiaryTaxNetOperatingLossCarryForwardsAnnualLimitAmountUnderInternalRevenueCode"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_IncomeTaxesDetailsLineItems" xlink:to="idt_TotalSubsidiaryTaxNetOperatingLossCarryForwardsAnnualLimitAmountUnderInternalRevenueCode" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ValuationAllowancesAndReservesDeductions" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDeductions"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_IncomeTaxesDetailsLineItems" xlink:to="us-gaap_ValuationAllowancesAndReservesDeductions" order="9" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_TaxCreditCarryforwardAmount" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxCreditCarryforwardAmount"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_IncomeTaxesDetailsLineItems" xlink:to="us-gaap_TaxCreditCarryforwardAmount" order="10" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_TaxCreditCarryforwardDescription" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TaxCreditCarryforwardDescription"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_IncomeTaxesDetailsLineItems" xlink:to="us-gaap_TaxCreditCarryforwardDescription" order="11" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/EquityDetails">
<loc xlink:type="locator" xlink:label="idt_EquityDetailsLineItems" xlink:href="idt-20200731.xsd#idt_EquityDetailsLineItems"/>
<loc xlink:type="locator" xlink:label="idt_EquityDetailsTable" xlink:href="idt-20200731.xsd#idt_EquityDetailsTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_EquityDetailsLineItems" xlink:to="idt_EquityDetailsTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementClassOfStockAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_EquityDetailsTable" xlink:to="us-gaap_StatementClassOfStockAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareRepurchaseProgramAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareRepurchaseProgramAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_EquityDetailsTable" xlink:to="us-gaap_ShareRepurchaseProgramAxis" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareRepurchaseProgramDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_ShareRepurchaseProgramAxis" xlink:to="us-gaap_ShareRepurchaseProgramDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareRepurchaseProgramDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_ShareRepurchaseProgramAxis" xlink:to="us-gaap_ShareRepurchaseProgramDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_TitleOfIndividualAxis" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_TitleOfIndividualAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_EquityDetailsTable" xlink:to="srt_TitleOfIndividualAxis" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_TitleOfIndividualWithRelationshipToEntityDomain" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_TitleOfIndividualAxis" xlink:to="srt_TitleOfIndividualWithRelationshipToEntityDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_TitleOfIndividualWithRelationshipToEntityDomain_0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="srt_TitleOfIndividualAxis" xlink:to="srt_TitleOfIndividualWithRelationshipToEntityDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AwardTypeAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardTypeAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_EquityDetailsTable" xlink:to="us-gaap_AwardTypeAxis" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_EquityDetailsTable" xlink:to="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SubsequentEventTypeAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_EquityDetailsTable" xlink:to="us-gaap_SubsequentEventTypeAxis" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SubsequentEventTypeDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SubsequentEventTypeDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementEquityComponentsAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_EquityDetailsTable" xlink:to="us-gaap_StatementEquityComponentsAxis" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EquityComponentDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EquityComponentDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommonClassBMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonClassBMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonClassBMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_NoncontrollingInterestMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoncontrollingInterestMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_NoncontrollingInterestMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_HowardSJonasMember" xlink:href="idt-20200731.xsd#idt_HowardSJonasMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="idt_HowardSJonasMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_FiscaLTwentyTwentyOneMember" xlink:href="idt-20200731.xsd#idt_FiscaLTwentyTwentyOneMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="idt_FiscaLTwentyTwentyOneMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_EmployeesMember" xlink:href="idt-20200731.xsd#idt_EmployeesMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_TitleOfIndividualWithRelationshipToEntityDomain" xlink:to="idt_EmployeesMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_StockRepurchasesMember" xlink:href="idt-20200731.xsd#idt_StockRepurchasesMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareRepurchaseProgramDomain" xlink:to="idt_StockRepurchasesMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SubsequentEventMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SubsequentEventTypeDomain" xlink:to="us-gaap_SubsequentEventMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_TreasuryStockSharesAcquired" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockSharesAcquired"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityDetailsLineItems" xlink:to="us-gaap_TreasuryStockSharesAcquired" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_MinorityInterestDecrease" xlink:href="idt-20200731.xsd#idt_MinorityInterestDecrease"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityDetailsLineItems" xlink:to="idt_MinorityInterestDecrease" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StockIssuedDuringPeriodSharesTreasuryStockReissued" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesTreasuryStockReissued"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityDetailsLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesTreasuryStockReissued" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StockIssuedDuringPeriodValueTreasuryStockReissued" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueTreasuryStockReissued"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityDetailsLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueTreasuryStockReissued" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_StockIssuedDuringPeriodPricePerShareForTreasuryStockReissued" xlink:href="idt-20200731.xsd#idt_StockIssuedDuringPeriodPricePerShareForTreasuryStockReissued"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityDetailsLineItems" xlink:to="idt_StockIssuedDuringPeriodPricePerShareForTreasuryStockReissued" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityDetailsLineItems" xlink:to="us-gaap_ProceedsFromIssuanceOfCommonStock" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ReductionToProceedsFromIssuanceOfCommonStock" xlink:href="idt-20200731.xsd#idt_ReductionToProceedsFromIssuanceOfCommonStock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityDetailsLineItems" xlink:to="idt_ReductionToProceedsFromIssuanceOfCommonStock" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityDetailsLineItems" xlink:to="us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityDetailsLineItems" xlink:to="us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased" order="9" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityDetailsLineItems" xlink:to="us-gaap_TreasuryStockValueAcquiredCostMethod" order="10" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_EquityDetailsLineItems" xlink:to="us-gaap_StockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased" order="11" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/StockBasedCompensationDetails">
<loc xlink:type="locator" xlink:label="idt_StockBasedCompensationDetailsLineItems" xlink:href="idt-20200731.xsd#idt_StockBasedCompensationDetailsLineItems"/>
<loc xlink:type="locator" xlink:label="idt_StockBasedCompensationDetailsTable" xlink:href="idt-20200731.xsd#idt_StockBasedCompensationDetailsTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_StockBasedCompensationDetailsLineItems" xlink:to="idt_StockBasedCompensationDetailsTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementClassOfStockAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_StockBasedCompensationDetailsTable" xlink:to="us-gaap_StatementClassOfStockAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementEquityComponentsAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_StockBasedCompensationDetailsTable" xlink:to="us-gaap_StatementEquityComponentsAxis" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EquityComponentDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EquityComponentDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AwardTypeAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardTypeAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_StockBasedCompensationDetailsTable" xlink:to="us-gaap_AwardTypeAxis" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SubsequentEventTypeAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_StockBasedCompensationDetailsTable" xlink:to="us-gaap_SubsequentEventTypeAxis" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SubsequentEventTypeDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SubsequentEventTypeDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommonClassBMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonClassBMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonClassBMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_OptionMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OptionMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="us-gaap_OptionMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RestrictedStockMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestrictedStockMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="us-gaap_RestrictedStockMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_DeferredStockUnitsMember" xlink:href="idt-20200731.xsd#idt_DeferredStockUnitsMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="idt_DeferredStockUnitsMember" order="2" xbrldt:closed="true"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="idt_DeferredStockUnitsMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SubsequentEventMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SubsequentEventTypeDomain" xlink:to="us-gaap_SubsequentEventMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRights" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRights"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRights" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsLineItems" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsLineItems" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDescription" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDescription"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDescription" order="9" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" order="10" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestingDeferredInPeriod" xlink:href="idt-20200731.xsd#idt_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestingDeferredInPeriod"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsLineItems" xlink:to="idt_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestingDeferredInPeriod" order="11" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_RestrictedEquityVestingConditionBusinessUnitFairValue" xlink:href="idt-20200731.xsd#idt_RestrictedEquityVestingConditionBusinessUnitFairValue"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_StockBasedCompensationDetailsLineItems" xlink:to="idt_RestrictedEquityVestingConditionBusinessUnitFairValue" order="12" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/CommitmentsandContingenciesDetails">
<loc xlink:type="locator" xlink:label="idt_CommitmentsandContingenciesDetailsLineItems" xlink:href="idt-20200731.xsd#idt_CommitmentsandContingenciesDetailsLineItems"/>
<loc xlink:type="locator" xlink:label="idt_CommitmentsandContingenciesDetailsTable" xlink:href="idt-20200731.xsd#idt_CommitmentsandContingenciesDetailsTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_CommitmentsandContingenciesDetailsLineItems" xlink:to="idt_CommitmentsandContingenciesDetailsTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_LegalEntityAxis" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_CommitmentsandContingenciesDetailsTable" xlink:to="dei_LegalEntityAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityDomain" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="dei_LegalEntityAxis" xlink:to="dei_EntityDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityDomain_0" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="dei_LegalEntityAxis" xlink:to="dei_EntityDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_TelecomOperatorMember" xlink:href="idt-20200731.xsd#idt_TelecomOperatorMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="idt_TelecomOperatorMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_AccruedLiabilitiesCurrentAndNoncurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccruedLiabilitiesCurrentAndNoncurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_CommitmentsandContingenciesDetailsLineItems" xlink:to="us-gaap_AccruedLiabilitiesCurrentAndNoncurrent" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_PurchaseObligation" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PurchaseObligation"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_CommitmentsandContingenciesDetailsLineItems" xlink:to="us-gaap_PurchaseObligation" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_EscrowDeposit" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EscrowDeposit"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_CommitmentsandContingenciesDetailsLineItems" xlink:to="us-gaap_EscrowDeposit" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SecurityDeposit" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SecurityDeposit"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_CommitmentsandContingenciesDetailsLineItems" xlink:to="us-gaap_SecurityDeposit" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_PerformanceBondsOutstanding" xlink:href="idt-20200731.xsd#idt_PerformanceBondsOutstanding"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_CommitmentsandContingenciesDetailsLineItems" xlink:to="idt_PerformanceBondsOutstanding" order="5" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/RelatedPartyTransactionsDetails">
<loc xlink:type="locator" xlink:label="idt_RelatedPartyTransactionsDetailsLineItems" xlink:href="idt-20200731.xsd#idt_RelatedPartyTransactionsDetailsLineItems"/>
<loc xlink:type="locator" xlink:label="idt_RelatedPartyTransactionsDetailsTable" xlink:href="idt-20200731.xsd#idt_RelatedPartyTransactionsDetailsTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="idt_RelatedPartyTransactionsDetailsLineItems" xlink:to="idt_RelatedPartyTransactionsDetailsTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_LitigationCaseAxis" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_LitigationCaseAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_RelatedPartyTransactionsDetailsTable" xlink:to="srt_LitigationCaseAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_LitigationCaseTypeDomain" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_LitigationCaseTypeDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_LitigationCaseAxis" xlink:to="srt_LitigationCaseTypeDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="srt_LitigationCaseTypeDomain_0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_LitigationCaseTypeDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="srt_LitigationCaseAxis" xlink:to="srt_LitigationCaseTypeDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_RelatedPartyTransactionsDetailsTable" xlink:to="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyTransactionAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_RelatedPartyTransactionsDetailsTable" xlink:to="us-gaap_RelatedPartyTransactionAxis" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyTransactionDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RelatedPartyTransactionAxis" xlink:to="us-gaap_RelatedPartyTransactionDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyTransactionDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_RelatedPartyTransactionAxis" xlink:to="us-gaap_RelatedPartyTransactionDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SubsequentEventTypeAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="idt_RelatedPartyTransactionsDetailsTable" xlink:to="us-gaap_SubsequentEventTypeAxis" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SubsequentEventTypeDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SubsequentEventTypeDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_RafaelSpinOffMember" xlink:href="idt-20200731.xsd#idt_RafaelSpinOffMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="idt_RafaelSpinOffMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_JonasMember" xlink:href="idt-20200731.xsd#idt_JonasMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="idt_JonasMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_IgmBrokerageMember" xlink:href="idt-20200731.xsd#idt_IgmBrokerageMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="idt_IgmBrokerageMember" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_GenieAndSubsidiarieMember" xlink:href="idt-20200731.xsd#idt_GenieAndSubsidiarieMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_LitigationCaseTypeDomain" xlink:to="idt_GenieAndSubsidiarieMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_ZedgeIncMember" xlink:href="idt-20200731.xsd#idt_ZedgeIncMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionDomain" xlink:to="idt_ZedgeIncMember" order="0" xbrldt:closed="true"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionDomain" xlink:to="idt_JonasMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_MasonAndCompanyConsultingMember" xlink:href="idt-20200731.xsd#idt_MasonAndCompanyConsultingMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionDomain" xlink:to="idt_MasonAndCompanyConsultingMember" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_SubsequentEventMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SubsequentEventTypeDomain" xlink:to="us-gaap_SubsequentEventMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CostsAndExpensesRelatedParty" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CostsAndExpensesRelatedParty"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_RelatedPartyTransactionsDetailsLineItems" xlink:to="us-gaap_CostsAndExpensesRelatedParty" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_RelatedPartyTransactionsCashCollectedFromThirdPartyTenants" xlink:href="idt-20200731.xsd#idt_RelatedPartyTransactionsCashCollectedFromThirdPartyTenants"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_RelatedPartyTransactionsDetailsLineItems" xlink:to="idt_RelatedPartyTransactionsCashCollectedFromThirdPartyTenants" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DueFromOtherRelatedPartiesCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DueFromOtherRelatedPartiesCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_RelatedPartyTransactionsDetailsLineItems" xlink:to="us-gaap_DueFromOtherRelatedPartiesCurrent" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_NumberOfRelatedPartySharesReceivesInConnectionWithRestrictedStock" xlink:href="idt-20200731.xsd#idt_NumberOfRelatedPartySharesReceivesInConnectionWithRestrictedStock"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_RelatedPartyTransactionsDetailsLineItems" xlink:to="idt_NumberOfRelatedPartySharesReceivesInConnectionWithRestrictedStock" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_RelatedPartyTransactionBillingsToRelatedPartyForServices" xlink:href="idt-20200731.xsd#idt_RelatedPartyTransactionBillingsToRelatedPartyForServices"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_RelatedPartyTransactionsDetailsLineItems" xlink:to="idt_RelatedPartyTransactionBillingsToRelatedPartyForServices" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_RelatedPartyTransactionBillingsAdjustmentToRelatedPartyForServices" xlink:href="idt-20200731.xsd#idt_RelatedPartyTransactionBillingsAdjustmentToRelatedPartyForServices"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_RelatedPartyTransactionsDetailsLineItems" xlink:to="idt_RelatedPartyTransactionBillingsAdjustmentToRelatedPartyForServices" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_RelatedPartyTransactionsDetailsLineItems" xlink:to="us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_LeaseExpirationDescription" xlink:href="idt-20200731.xsd#idt_LeaseExpirationDescription"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_RelatedPartyTransactionsDetailsLineItems" xlink:to="idt_LeaseExpirationDescription" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_RelatedPartyTransactionLeaseAnnualRentPaymentsToRelatedParty" xlink:href="idt-20200731.xsd#idt_RelatedPartyTransactionLeaseAnnualRentPaymentsToRelatedParty"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_RelatedPartyTransactionsDetailsLineItems" xlink:to="idt_RelatedPartyTransactionLeaseAnnualRentPaymentsToRelatedParty" order="9" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DueFromEmployeesCurrent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DueFromEmployeesCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="idt_RelatedPartyTransactionsDetailsLineItems" xlink:to="us-gaap_DueFromEmployeesCurrent" order="10" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/DefinedContributionPlansDetails">
<loc xlink:type="locator" xlink:label="us-gaap_DisclosureTextBlockSupplementAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisclosureTextBlockSupplementAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DisclosureTextBlockSupplementAbstract" xlink:to="us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DisclosureTextBlockSupplementAbstract" xlink:to="us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_DefinedContributionPlanEmployerMatchingContributionLimitPercent" xlink:href="idt-20200731.xsd#idt_DefinedContributionPlanEmployerMatchingContributionLimitPercent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DisclosureTextBlockSupplementAbstract" xlink:to="idt_DefinedContributionPlanEmployerMatchingContributionLimitPercent" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="idt_DefinedContributionPlanEmployerDiscretionaryContributionVestingPeriod" xlink:href="idt-20200731.xsd#idt_DefinedContributionPlanEmployerDiscretionaryContributionVestingPeriod"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DisclosureTextBlockSupplementAbstract" xlink:to="idt_DefinedContributionPlanEmployerDiscretionaryContributionVestingPeriod" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_DefinedContributionPlanCostRecognized" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedContributionPlanCostRecognized"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DisclosureTextBlockSupplementAbstract" xlink:to="us-gaap_DefinedContributionPlanCostRecognized" order="4" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/BusinessSegmentInformationDetails">
<loc xlink:type="locator" xlink:label="us-gaap_SegmentReportingAbstract" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingAbstract"/>
<loc xlink:type="locator" xlink:label="us-gaap_NumberOfReportableSegments" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NumberOfReportableSegments"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SegmentReportingAbstract" xlink:to="us-gaap_NumberOfReportableSegments" order="0" xbrldt:closed="true"/>
</definitionLink>
<definitionLink xlink:type="extended" xlink:role="http://www.www.idt.net/role/DocumentAndEntityInformation">
<loc xlink:type="locator" xlink:label="dei_DocumentInformationLineItems" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentInformationLineItems"/>
<loc xlink:type="locator" xlink:label="dei_DocumentInformationTable" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentInformationTable"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentInformationTable" order="0" xbrldt:contextElement="segment" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_StatementClassOfStockAxis" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="dei_DocumentInformationTable" xlink:to="us-gaap_StatementClassOfStockAxis" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_ClassOfStockDomain_0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain_0" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommonClassBMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonClassBMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonClassBMember" order="0" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="us-gaap_CommonClassAMember" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonClassAMember"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_CommonClassAMember" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityRegistrantName" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityRegistrantName"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityRegistrantName" order="1" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_TradingSymbol" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_TradingSymbol"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_TradingSymbol" order="2" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_DocumentType" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentType"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentType" order="3" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_CurrentFiscalYearEndDate" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_CurrentFiscalYearEndDate"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_CurrentFiscalYearEndDate" order="4" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityCommonStockSharesOutstanding" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityCommonStockSharesOutstanding"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityCommonStockSharesOutstanding" order="5" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityPublicFloat" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityPublicFloat"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityPublicFloat" order="6" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_AmendmentFlag" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_AmendmentFlag"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_AmendmentFlag" order="7" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityCentralIndexKey" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityCentralIndexKey"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityCentralIndexKey" order="8" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityCurrentReportingStatus" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityCurrentReportingStatus"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityCurrentReportingStatus" order="9" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityVoluntaryFilers" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityVoluntaryFilers"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityVoluntaryFilers" order="10" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityFilerCategory" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityFilerCategory"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityFilerCategory" order="11" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityWellKnownSeasonedIssuer" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityWellKnownSeasonedIssuer"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityWellKnownSeasonedIssuer" order="12" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_DocumentPeriodEndDate" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentPeriodEndDate"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentPeriodEndDate" order="13" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_DocumentFiscalYearFocus" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentFiscalYearFocus"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentFiscalYearFocus" order="14" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_DocumentFiscalPeriodFocus" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentFiscalPeriodFocus"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentFiscalPeriodFocus" order="15" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntitySmallBusiness" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntitySmallBusiness"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntitySmallBusiness" order="16" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityEmergingGrowthCompany" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityEmergingGrowthCompany"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityEmergingGrowthCompany" order="17" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityShellCompany" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityShellCompany"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityShellCompany" order="18" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_DocumentAnnualReport" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentAnnualReport"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentAnnualReport" order="19" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_DocumentTransitionReport" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentTransitionReport"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentTransitionReport" order="20" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityFileNumber" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityFileNumber"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityFileNumber" order="21" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityIncorporationStateCountryCode" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityIncorporationStateCountryCode"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityIncorporationStateCountryCode" order="22" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityTaxIdentificationNumber" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityTaxIdentificationNumber"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityTaxIdentificationNumber" order="23" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityAddressAddressLine1" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressAddressLine1"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityAddressAddressLine1" order="24" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityAddressCityOrTown" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressCityOrTown"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityAddressCityOrTown" order="25" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityAddressStateOrProvince" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressStateOrProvince"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityAddressStateOrProvince" order="26" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityAddressPostalZipCode" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressPostalZipCode"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityAddressPostalZipCode" order="27" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_CityAreaCode" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_CityAreaCode"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_CityAreaCode" order="28" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_LocalPhoneNumber" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LocalPhoneNumber"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_LocalPhoneNumber" order="29" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_Security12gTitle" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_Security12gTitle"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_Security12gTitle" order="30" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_SecurityExchangeName" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_SecurityExchangeName"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_SecurityExchangeName" order="31" xbrldt:closed="true"/>
<loc xlink:type="locator" xlink:label="dei_EntityInteractiveDataCurrent" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityInteractiveDataCurrent"/>
<definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityInteractiveDataCurrent" order="32" xbrldt:closed="true"/>
</definitionLink>
</linkbase>


1 Subsequent Filing that References this Filing

  As Of               Filer                 Filing    For·On·As Docs:Size             Issuer                      Filing Agent

12/22/20  Idt Corp.                         10-K/A      7/31/20   12:298K                                   EdgarAgents LLC/FA


8 Previous Filings that this Filing References

  As Of               Filer                 Filing    For·On·As Docs:Size             Issuer                      Filing Agent

 4/07/20  Idt Corp.                         8-K:5,9     4/06/20    2:123K                                   EdgarAgents LLC/FA
12/05/17  Idt Corp.                         8-K:2,5,9  12/05/17    3:339K                                   EdgarAgents LLC/FA
10/16/17  Idt Corp.                         10-K        7/31/17  131:9.7M                                   EdgarAgents LLC/FA
12/20/16  Idt Corp.                         8-K:5,9    12/14/16    2:105K                                   EdgarAgents LLC/FA
10/14/16  Idt Corp.                         S-8        10/14/16    4:233K                                   EdgarAgents LLC/FA
 1/14/15  Idt Corp.                         8-K:5,9     1/12/15    2:94K                                    EdgarAgents LLC/FA
11/05/13  Idt Corp.                         DEF 14A    12/16/13    1:569K                                   Donnelley … Solutions/FA
 4/05/11  Idt Corp.                         8-K:3,5,8,9 4/04/11    3:136K                                   EdgarAgents LLC/FA
Top
Filing Submission 0001213900-20-031279   –   Alternative Formats (Word / Rich Text, HTML, Plain Text, et al.)

Copyright © 2024 Fran Finnegan & Company LLC – All Rights Reserved.
AboutPrivacyRedactionsHelp — Wed., May 1, 10:20:56.2am ET