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

Idt Corp – ‘10-Q’ for 4/30/20 – ‘EX-101.DEF’

On:  Tuesday, 6/9/20, at 1:55pm ET   ·   For:  4/30/20   ·   Accession #:  1213900-20-14476   ·   File #:  1-16371

Previous ‘10-Q’:  ‘10-Q’ on 3/11/20 for 1/31/20   ·   Next:  ‘10-Q’ on 12/10/20 for 10/31/20   ·   Latest:  ‘10-Q’ on 3/11/24 for 1/31/24

Find Words in Filings emoji
 
  in    Show  and   Hints

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

 6/09/20  Idt Corp                          10-Q        4/30/20   90:4.8M                                   Edgar Agents LLC/FA

Quarterly Report   —   Form 10-Q   —   Sect. 13 / 15(d) – SEA’34
Filing Table of Contents

Document/Exhibit                   Description                      Pages   Size 

 1: 10-Q        Quarterly Report                                    HTML    454K 
 2: EX-31.1     Certification -- §302 - SOA'02                      HTML     27K 
 3: EX-31.2     Certification -- §302 - SOA'02                      HTML     27K 
 4: EX-32.1     Certification -- §906 - SOA'02                      HTML     23K 
 5: EX-32.2     Certification -- §906 - SOA'02                      HTML     23K 
80: R1          Document and Entity Information                     HTML     57K 
36: R2          Consolidated Balance Sheets                         HTML    127K 
24: R3          Consolidated Balance Sheets (Parenthetical)         HTML     47K 
50: R4          Consolidated Statements of Operations (Unaudited)   HTML     95K 
77: R5          Consolidated Statements of Comprehensive (Loss)     HTML     52K 
                Income (Unaudited)                                               
33: R6          Consolidated Statements of Equity (Unaudited)       HTML     66K 
21: R7          Consolidated Statements of Cash Flows (Unaudited)   HTML    114K 
49: R8          Basis of Presentation                               HTML     28K 
81: R9          Revenue Recognition                                 HTML     82K 
35: R10         Leases                                              HTML     44K 
23: R11         Cash, Cash Equivalents, and Restricted Cash and     HTML     30K 
                Cash Equivalents                                                 
52: R12         Debt Securities                                     HTML     45K 
79: R13         Equity Investments                                  HTML     48K 
34: R14         Fair Value Measurements                             HTML     59K 
22: R15         Acquisitions                                        HTML     36K 
51: R16         Other Operating Expense, Net                        HTML     52K 
78: R17         Equity                                              HTML     34K 
32: R18         Earnings (Loss) Per Share                           HTML     39K 
25: R19         Note Payable and Revolving Credit Loan Payable      HTML     28K 
67: R20         Accumulated Other Comprehensive Loss                HTML     29K 
76: R21         Business Segment Information                        HTML     41K 
47: R22         Commitments and Contingencies                       HTML     50K 
18: R23         Other (Expense) Income, Net                         HTML     31K 
66: R24         Defined Contribution Plan                           HTML     27K 
75: R25         Recently Issued Accounting Standards Not Yet        HTML     29K 
                Adopted                                                          
46: R26         Revenue Recognition (Tables)                        HTML     78K 
17: R27         Leases (Tables)                                     HTML     41K 
68: R28         Cash, Cash Equivalents, and Restricted Cash and     HTML     29K 
                Cash Equivalents (Tables)                                        
74: R29         Debt Securities (Tables)                            HTML     44K 
82: R30         Equity Investments (Tables)                         HTML     47K 
54: R31         Fair Value Measurements (Tables)                    HTML     60K 
19: R32         Acquisitions (Tables)                               HTML     41K 
30: R33         Other Operating Expense, Net (Tables)               HTML     50K 
83: R34         Earnings (Loss) Per Share (Tables)                  HTML     38K 
55: R35         Accumulated Other Comprehensive Loss (Tables)       HTML     29K 
20: R36         Business Segment Information (Tables)               HTML     39K 
31: R37         Other (Expense) Income, Net (Tables)                HTML     30K 
84: R38         Revenue Recognition (Details)                       HTML     48K 
53: R39         Revenue Recognition (Details 1)                     HTML     54K 
69: R40         Revenue Recognition (Details 2)                     HTML     27K 
62: R41         Revenue Recognition (Details 3)                     HTML     30K 
15: R42         Revenue Recognition (Details 4)                     HTML     25K 
44: R43         Leases (Details)                                    HTML     39K 
70: R44         Leases (Details 1)                                  HTML     29K 
63: R45         Leases (Details 2)                                  HTML     43K 
16: R46         Leases (Details Textual)                            HTML     37K 
45: R47         Cash, Cash Equivalents, and Restricted Cash and     HTML     34K 
                Cash Equivalents (Details)                                       
71: R48         Cash, Cash Equivalents, and Restricted Cash and     HTML     29K 
                Cash Equivalents (Details Textual)                               
60: R49         Debt Securities (Details)                           HTML     41K 
57: R50         Debt Securities (Details 1)                         HTML     34K 
88: R51         Debt Securities (Details 2)                         HTML     29K 
40: R52         Debt Securities (Details Textual)                   HTML     30K 
29: R53         Equity Investments (Details)                        HTML     42K 
56: R54         Equity Investments (Details 1)                      HTML     36K 
86: R55         Equity Investments (Details 2)                      HTML     29K 
39: R56         Equity Investments (Details Textual)                HTML     43K 
28: R57         Fair Value Measurements (Details)                   HTML     48K 
58: R58         Fair Value Measurements (Details 1)                 HTML     35K 
85: R59         Fair Value Measurements (Details 2)                 HTML     35K 
43: R60         Fair Value Measurements (Details Textual)           HTML     24K 
13: R61         Acquisitions (Details)                              HTML     30K 
65: R62         Acquisitions (Details 1)                            HTML     55K 
73: R63         Acquisitions (Details Textual)                      HTML     34K 
42: R64         Other Operating Expense, Net (Details)              HTML     34K 
12: R65         Other Operating Expense, Net (Details 1)            HTML     66K 
64: R66         Other Operating Expense, Net (Details Textual)      HTML     33K 
72: R67         Equity (Details)                                    HTML     75K 
41: R68         Earnings (Loss) Per Share (Details)                 HTML     37K 
14: R69         Earnings (Loss) Per Share (Details 1)               HTML     31K 
26: R70         Note Payable and Revolving Credit Loan Payable      HTML     39K 
                (Details)                                                        
37: R71         Accumulated Other Comprehensive Loss (Details)      HTML     41K 
89: R72         Business Segment Information (Details)              HTML     41K 
59: R73         Business Segment Information (Details Textual)      HTML     24K 
27: R74         Commitments and Contingencies (Details)             HTML     40K 
38: R75         Other (Expense) Income, Net (Details)               HTML     34K 
90: R76         Defined Contribution Plan (Details)                 HTML     32K 
87: XML         IDEA XML File -- Filing Summary                      XML    164K 
61: EXCEL       IDEA Workbook of Financial Reports                  XLSX     85K 
 6: EX-101.INS  XBRL Instance -- idt-20200430                        XML   1.66M 
 8: EX-101.CAL  XBRL Calculations -- idt-20200430_cal                XML    228K 
 9: EX-101.DEF  XBRL Definitions -- idt-20200430_def                 XML    521K 
10: EX-101.LAB  XBRL Labels -- idt-20200430_lab                      XML   1.01M 
11: EX-101.PRE  XBRL Presentations -- idt-20200430_pre               XML    773K 
 7: EX-101.SCH  XBRL Schema -- idt-20200430                          XSD    204K 
48: ZIP         XBRL Zipped Folder -- 0001213900-20-014476-xbrl      Zip    134K 


‘EX-101.DEF’   —   XBRL Definitions — idt-20200430_def


This Exhibit is an XBRL XML File.


                                                                                                                                                                                
<?xml version="1.0" standalone="no" encoding="windows-1252"?>
<!-- Field: Doc-Info; Name: Generator; Value: GoXBRL; Version: 5.3a -->
<!-- Field: Doc-Info; Name: VendorURI; Value: http://www.novaworks.co -->
<!-- Field: Doc-Info; Name: Source; Value: idt%2D20200430.xfr; Date: 2020%2D06%2D09T00:57:08Z -->
<!-- Field: Doc-Info; Name: Status; Value: 0x00000000 -->
<link:linkbase xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xbrli="http://www.xbrl.org/2003/instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
<link:roleRef roleURI="http://idt.net/role/DocumentAndEntityInformation" xlink:href="idt-20200430.xsd#DocumentAndEntityInformation" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/BalanceSheets" xlink:href="idt-20200430.xsd#BalanceSheets" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/BalanceSheetsParenthetical" xlink:href="idt-20200430.xsd#BalanceSheetsParenthetical" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/StatementsOfOperations" xlink:href="idt-20200430.xsd#StatementsOfOperations" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/StatementsOfComprehensiveLossIncome" xlink:href="idt-20200430.xsd#StatementsOfComprehensiveLossIncome" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/ConsolidatedStatementsOfEquity" xlink:href="idt-20200430.xsd#ConsolidatedStatementsOfEquity" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/StatementsOfCashFlows" xlink:href="idt-20200430.xsd#StatementsOfCashFlows" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/BasisOfPresentation" xlink:href="idt-20200430.xsd#BasisOfPresentation" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/RevenueRecognition" xlink:href="idt-20200430.xsd#RevenueRecognition" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/Leases" xlink:href="idt-20200430.xsd#Leases" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/CashCashEquivalentsAndRestrictedCashAndCashEquivalents" xlink:href="idt-20200430.xsd#CashCashEquivalentsAndRestrictedCashAndCashEquivalents" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/DebtSecurities" xlink:href="idt-20200430.xsd#DebtSecurities" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/EquityInvestments" xlink:href="idt-20200430.xsd#EquityInvestments" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/FairValueMeasurements" xlink:href="idt-20200430.xsd#FairValueMeasurements" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/AcquisitionOfVersatureCorp." xlink:href="idt-20200430.xsd#AcquisitionOfVersatureCorp." xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/OtherOperatingExpenseNet" xlink:href="idt-20200430.xsd#OtherOperatingExpenseNet" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/Equity" xlink:href="idt-20200430.xsd#Equity" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/EarningsLossPerShare" xlink:href="idt-20200430.xsd#EarningsLossPerShare" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/RevolvingCreditFacility" xlink:href="idt-20200430.xsd#RevolvingCreditFacility" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/AccumulatedOtherComprehensiveLoss" xlink:href="idt-20200430.xsd#AccumulatedOtherComprehensiveLoss" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/BusinessSegmentInformation" xlink:href="idt-20200430.xsd#BusinessSegmentInformation" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/CommitmentsAndContingencies" xlink:href="idt-20200430.xsd#CommitmentsAndContingencies" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/OtherExpenseIncomeNet" xlink:href="idt-20200430.xsd#OtherExpenseIncomeNet" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/DefinedContributionPlan" xlink:href="idt-20200430.xsd#DefinedContributionPlan" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/RecentlyIssuedAccountingStandardNotYetAdopted" xlink:href="idt-20200430.xsd#RecentlyIssuedAccountingStandardNotYetAdopted" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/RevenueRecognitionTables" xlink:href="idt-20200430.xsd#RevenueRecognitionTables" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/LeasesTables" xlink:href="idt-20200430.xsd#LeasesTables" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/CashCashEquivalentsAndRestrictedCashAndCashEquivalentsTables" xlink:href="idt-20200430.xsd#CashCashEquivalentsAndRestrictedCashAndCashEquivalentsTables" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/DebtSecuritiesTables" xlink:href="idt-20200430.xsd#DebtSecuritiesTables" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/EquityInvestmentsTables" xlink:href="idt-20200430.xsd#EquityInvestmentsTables" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/FairValueMeasurementsTables" xlink:href="idt-20200430.xsd#FairValueMeasurementsTables" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/AcquisitionOfVersatureCorp.Tables" xlink:href="idt-20200430.xsd#AcquisitionOfVersatureCorp.Tables" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/OtherOperatingExpenseNetTables" xlink:href="idt-20200430.xsd#OtherOperatingExpenseNetTables" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/EarningsLossPerShareTables" xlink:href="idt-20200430.xsd#EarningsLossPerShareTables" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/AccumulatedOtherComprehensiveLossTables" xlink:href="idt-20200430.xsd#AccumulatedOtherComprehensiveLossTables" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/BusinessSegmentInformationTables" xlink:href="idt-20200430.xsd#BusinessSegmentInformationTables" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/OtherExpenseIncomeNetTables" xlink:href="idt-20200430.xsd#OtherExpenseIncomeNetTables" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/RevenueRecognitionDetails" xlink:href="idt-20200430.xsd#RevenueRecognitionDetails" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/RevenueRecognitionDetails1" xlink:href="idt-20200430.xsd#RevenueRecognitionDetails1" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/RevenueRecognitionDetails2" xlink:href="idt-20200430.xsd#RevenueRecognitionDetails2" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/RevenueRecognitionDetails3" xlink:href="idt-20200430.xsd#RevenueRecognitionDetails3" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/RevenueRecognitionDetails4" xlink:href="idt-20200430.xsd#RevenueRecognitionDetails4" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/LeasesDetails" xlink:href="idt-20200430.xsd#LeasesDetails" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/LeasesDetails1" xlink:href="idt-20200430.xsd#LeasesDetails1" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/LeasesDetails2" xlink:href="idt-20200430.xsd#LeasesDetails2" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/LeasesDetailsTextual" xlink:href="idt-20200430.xsd#LeasesDetailsTextual" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/CashCashEquivalentsAndRestrictedCashAndCashEquivalentsDetails" xlink:href="idt-20200430.xsd#CashCashEquivalentsAndRestrictedCashAndCashEquivalentsDetails" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/CashCashEquivalentsAndRestrictedCashAndCashEquivalentsDetailsTextual" xlink:href="idt-20200430.xsd#CashCashEquivalentsAndRestrictedCashAndCashEquivalentsDetailsTextual" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/DebtSecuritiesDetails" xlink:href="idt-20200430.xsd#DebtSecuritiesDetails" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/DebtSecuritiesDetails1" xlink:href="idt-20200430.xsd#DebtSecuritiesDetails1" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/DebtSecuritiesDetails2" xlink:href="idt-20200430.xsd#DebtSecuritiesDetails2" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/DebtSecuritiesDetailsTextual" xlink:href="idt-20200430.xsd#DebtSecuritiesDetailsTextual" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/EquityInvestmentsDetails" xlink:href="idt-20200430.xsd#EquityInvestmentsDetails" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/EquityInvestmentsDetails1" xlink:href="idt-20200430.xsd#EquityInvestmentsDetails1" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/EquityInvestmentsDetails2" xlink:href="idt-20200430.xsd#EquityInvestmentsDetails2" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/EquityInvestmentsDetailsTextual" xlink:href="idt-20200430.xsd#EquityInvestmentsDetailsTextual" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/FairValueMeasurementsDetails" xlink:href="idt-20200430.xsd#FairValueMeasurementsDetails" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/FairValueMeasurementsDetails1" xlink:href="idt-20200430.xsd#FairValueMeasurementsDetails1" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/FairValueMeasurementsDetails2" xlink:href="idt-20200430.xsd#FairValueMeasurementsDetails2" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/FairValueMeasurementsDetailsTextual" xlink:href="idt-20200430.xsd#FairValueMeasurementsDetailsTextual" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/AcquisitionsDetails" xlink:href="idt-20200430.xsd#AcquisitionsDetails" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/AcquisitionsDetails1" xlink:href="idt-20200430.xsd#AcquisitionsDetails1" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/AcquisitionsDetailsTextual" xlink:href="idt-20200430.xsd#AcquisitionsDetailsTextual" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/OtherOperatingExpenseNetDetails" xlink:href="idt-20200430.xsd#OtherOperatingExpenseNetDetails" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/OtherOperatingExpenseNetDetails1" xlink:href="idt-20200430.xsd#OtherOperatingExpenseNetDetails1" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/OtherOperatingExpenseNetDetailsTextual" xlink:href="idt-20200430.xsd#OtherOperatingExpenseNetDetailsTextual" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/EquityDetails" xlink:href="idt-20200430.xsd#EquityDetails" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/EarningsLossPerShareDetails" xlink:href="idt-20200430.xsd#EarningsLossPerShareDetails" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/EarningsLossPerShareDetails1" xlink:href="idt-20200430.xsd#EarningsLossPerShareDetails1" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/NotePayableAndRevolvingCreditLoanPayableDetails" xlink:href="idt-20200430.xsd#NotePayableAndRevolvingCreditLoanPayableDetails" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/AccumulatedOtherComprehensiveLossDetails" xlink:href="idt-20200430.xsd#AccumulatedOtherComprehensiveLossDetails" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/BusinessSegmentInformationDetails" xlink:href="idt-20200430.xsd#BusinessSegmentInformationDetails" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/BusinessSegmentInformationDetailsTextual" xlink:href="idt-20200430.xsd#BusinessSegmentInformationDetailsTextual" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/CommitmentsAndContingenciesDetails" xlink:href="idt-20200430.xsd#CommitmentsAndContingenciesDetails" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/OtherExpenseIncomeNetDetails" xlink:href="idt-20200430.xsd#OtherExpenseIncomeNetDetails" xlink:type="simple"/>
<link:roleRef roleURI="http://idt.net/role/DefinedContributionPlanDetails" xlink:href="idt-20200430.xsd#DefinedContributionPlanDetails" xlink:type="simple"/>
<link: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"/>
<link: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"/>
<link: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"/>
<link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" arcroleURI="http://xbrl.org/int/dim/arcrole/all"/>
<link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#notAll" arcroleURI="http://xbrl.org/int/dim/arcrole/notAll"/>
<link: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"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/DocumentAndEntityInformation" xlink:title="00000001 - Document - Document and Entity Information">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaapStatementLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaapStatementTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapStatementTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaapStatementClassOfStockAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapStatementTable" xlink:to="loc_us-gaapStatementClassOfStockAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaapClassOfStockDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapStatementClassOfStockAxis" xlink:to="loc_us-gaapClassOfStockDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaapClassOfStockDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementClassOfStockAxis" xlink:to="loc_us-gaapClassOfStockDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonClassAMember" xlink:label="loc_us-gaapCommonClassAMember_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapClassOfStockDomain" xlink:to="loc_us-gaapCommonClassAMember_10" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonClassBMember" xlink:label="loc_us-gaapCommonClassBMember_20"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapClassOfStockDomain" xlink:to="loc_us-gaapCommonClassBMember_20" xlink:type="arc" order="21"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityRegistrantName" xlink:label="loc_deiEntityRegistrantName_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_deiEntityRegistrantName_40" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityCentralIndexKey" xlink:label="loc_deiEntityCentralIndexKey_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_deiEntityCentralIndexKey_40" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_AmendmentFlag" xlink:label="loc_deiAmendmentFlag_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_deiAmendmentFlag_40" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_CurrentFiscalYearEndDate" xlink:label="loc_deiCurrentFiscalYearEndDate_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_deiCurrentFiscalYearEndDate_40" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentType" xlink:label="loc_deiDocumentType_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_deiDocumentType_40" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentPeriodEndDate" xlink:label="loc_deiDocumentPeriodEndDate_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_deiDocumentPeriodEndDate_40" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentFiscalPeriodFocus" xlink:label="loc_deiDocumentFiscalPeriodFocus_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_deiDocumentFiscalPeriodFocus_40" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentFiscalYearFocus" xlink:label="loc_deiDocumentFiscalYearFocus_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_deiDocumentFiscalYearFocus_40" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityCurrentReportingStatus" xlink:label="loc_deiEntityCurrentReportingStatus_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_deiEntityCurrentReportingStatus_40" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityFilerCategory" xlink:label="loc_deiEntityFilerCategory_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_deiEntityFilerCategory_40" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntitySmallBusiness" xlink:label="loc_deiEntitySmallBusiness_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_deiEntitySmallBusiness_40" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityShellCompany" xlink:label="loc_deiEntityShellCompany_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_deiEntityShellCompany_40" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityEmergingGrowthCompany" xlink:label="loc_deiEntityEmergingGrowthCompany_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_deiEntityEmergingGrowthCompany_40" xlink:type="arc" order="12"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityFileNumber" xlink:label="loc_deiEntityFileNumber_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_deiEntityFileNumber_40" xlink:type="arc" order="13"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityInteractiveDataCurrent" xlink:label="loc_deiEntityInteractiveDataCurrent_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_deiEntityInteractiveDataCurrent_40" xlink:type="arc" order="14"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityIncorporationStateCountryCode" xlink:label="loc_deiEntityIncorporationStateCountryCode_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_deiEntityIncorporationStateCountryCode_40" xlink:type="arc" order="15"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityCommonStockSharesOutstanding" xlink:label="loc_deiEntityCommonStockSharesOutstanding_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_deiEntityCommonStockSharesOutstanding_40" xlink:type="arc" order="16"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/BalanceSheets" xlink:title="00000002 - Statement - Consolidated Balance Sheets">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaapStatementLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaapStatementTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapStatementTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaapStatementClassOfStockAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapStatementTable" xlink:to="loc_us-gaapStatementClassOfStockAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaapClassOfStockDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapStatementClassOfStockAxis" xlink:to="loc_us-gaapClassOfStockDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaapClassOfStockDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementClassOfStockAxis" xlink:to="loc_us-gaapClassOfStockDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonClassAMember" xlink:label="loc_us-gaapCommonClassAMember_20"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapClassOfStockDomain" xlink:to="loc_us-gaapCommonClassAMember_20" xlink:type="arc" order="21"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonClassBMember" xlink:label="loc_us-gaapCommonClassBMember_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapClassOfStockDomain" xlink:to="loc_us-gaapCommonClassBMember_40" xlink:type="arc" order="41"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetsAbstract" xlink:label="loc_us-gaapAssetsAbstract_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapAssetsAbstract_70" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetsCurrentAbstract" xlink:label="loc_us-gaapAssetsCurrentAbstract_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAssetsAbstract_70" xlink:to="loc_us-gaapAssetsCurrentAbstract_70" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaapCashAndCashEquivalentsAtCarryingValue_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAssetsCurrentAbstract_70" xlink:to="loc_us-gaapCashAndCashEquivalentsAtCarryingValue_70" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaapRestrictedCashAndCashEquivalentsAtCarryingValue_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAssetsCurrentAbstract_70" xlink:to="loc_us-gaapRestrictedCashAndCashEquivalentsAtCarryingValue_70" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtSecuritiesCurrent" xlink:label="loc_us-gaapDebtSecuritiesCurrent_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAssetsCurrentAbstract_70" xlink:to="loc_us-gaapDebtSecuritiesCurrent_70" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherShortTermInvestments" xlink:label="loc_us-gaapOtherShortTermInvestments_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAssetsCurrentAbstract_70" xlink:to="loc_us-gaapOtherShortTermInvestments_70" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivablesNetCurrent" xlink:label="loc_us-gaapReceivablesNetCurrent_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAssetsCurrentAbstract_70" xlink:to="loc_us-gaapReceivablesNetCurrent_70" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PrepaidExpenseCurrent" xlink:label="loc_us-gaapPrepaidExpenseCurrent_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAssetsCurrentAbstract_70" xlink:to="loc_us-gaapPrepaidExpenseCurrent_70" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherAssetsCurrent" xlink:label="loc_us-gaapOtherAssetsCurrent_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAssetsCurrentAbstract_70" xlink:to="loc_us-gaapOtherAssetsCurrent_70" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetsCurrent" xlink:label="loc_us-gaapAssetsCurrent_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAssetsCurrentAbstract_70" xlink:to="loc_us-gaapAssetsCurrent_70" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaapPropertyPlantAndEquipmentNet_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAssetsAbstract_70" xlink:to="loc_us-gaapPropertyPlantAndEquipmentNet_70" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaapGoodwill_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAssetsAbstract_70" xlink:to="loc_us-gaapGoodwill_70" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherIntangibleAssetsNet" xlink:label="loc_us-gaapOtherIntangibleAssetsNet_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAssetsAbstract_70" xlink:to="loc_us-gaapOtherIntangibleAssetsNet_70" xlink:type="arc" order="12"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermInvestments" xlink:label="loc_us-gaapLongTermInvestments_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAssetsAbstract_70" xlink:to="loc_us-gaapLongTermInvestments_70" xlink:type="arc" order="13"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset" xlink:label="loc_us-gaapOperatingLeaseRightOfUseAsset_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAssetsAbstract_70" xlink:to="loc_us-gaapOperatingLeaseRightOfUseAsset_70" xlink:type="arc" order="14"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DeferredIncomeTaxAssetsNet" xlink:label="loc_us-gaapDeferredIncomeTaxAssetsNet_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAssetsAbstract_70" xlink:to="loc_us-gaapDeferredIncomeTaxAssetsNet_70" xlink:type="arc" order="15"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherAssetsNoncurrent" xlink:label="loc_us-gaapOtherAssetsNoncurrent_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAssetsAbstract_70" xlink:to="loc_us-gaapOtherAssetsNoncurrent_70" xlink:type="arc" order="16"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Assets" xlink:label="loc_us-gaapAssets_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAssetsAbstract_70" xlink:to="loc_us-gaapAssets_70" xlink:type="arc" order="17"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:label="loc_us-gaapLiabilitiesAndStockholdersEquityAbstract_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapLiabilitiesAndStockholdersEquityAbstract_70" xlink:type="arc" order="18"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract" xlink:label="loc_us-gaapLiabilitiesCurrentAbstract_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapLiabilitiesAndStockholdersEquityAbstract_70" xlink:to="loc_us-gaapLiabilitiesCurrentAbstract_70" xlink:type="arc" order="19"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsPayableCurrent" xlink:label="loc_us-gaapAccountsPayableCurrent_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapLiabilitiesCurrentAbstract_70" xlink:to="loc_us-gaapAccountsPayableCurrent_70" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent" xlink:label="loc_us-gaapAccruedLiabilitiesCurrent_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapLiabilitiesCurrentAbstract_70" xlink:to="loc_us-gaapAccruedLiabilitiesCurrent_70" xlink:type="arc" order="21"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DeferredRevenueCurrent" xlink:label="loc_us-gaapDeferredRevenueCurrent_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapLiabilitiesCurrentAbstract_70" xlink:to="loc_us-gaapDeferredRevenueCurrent_70" xlink:type="arc" order="22"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DepositLiabilityCurrent" xlink:label="loc_us-gaapDepositLiabilityCurrent_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapLiabilitiesCurrentAbstract_70" xlink:to="loc_us-gaapDepositLiabilityCurrent_70" xlink:type="arc" order="23"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherLiabilitiesCurrent" xlink:label="loc_us-gaapOtherLiabilitiesCurrent_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapLiabilitiesCurrentAbstract_70" xlink:to="loc_us-gaapOtherLiabilitiesCurrent_70" xlink:type="arc" order="24"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:label="loc_us-gaapLiabilitiesCurrent_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapLiabilitiesCurrentAbstract_70" xlink:to="loc_us-gaapLiabilitiesCurrent_70" xlink:type="arc" order="25"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent" xlink:label="loc_us-gaapOperatingLeaseLiabilityNoncurrent_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapLiabilitiesCurrentAbstract_70" xlink:to="loc_us-gaapOperatingLeaseLiabilityNoncurrent_70" xlink:type="arc" order="26"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent" xlink:label="loc_us-gaapOtherLiabilitiesNoncurrent_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapLiabilitiesAndStockholdersEquityAbstract_70" xlink:to="loc_us-gaapOtherLiabilitiesNoncurrent_70" xlink:type="arc" order="27"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Liabilities" xlink:label="loc_us-gaapLiabilities_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapLiabilitiesAndStockholdersEquityAbstract_70" xlink:to="loc_us-gaapLiabilities_70" xlink:type="arc" order="28"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommitmentsAndContingencies" xlink:label="loc_us-gaapCommitmentsAndContingencies_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapLiabilitiesAndStockholdersEquityAbstract_70" xlink:to="loc_us-gaapCommitmentsAndContingencies_70" xlink:type="arc" order="29"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquityAbstract" xlink:label="loc_us-gaapStockholdersEquityAbstract_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapLiabilitiesAndStockholdersEquityAbstract_70" xlink:to="loc_us-gaapStockholdersEquityAbstract_70" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PreferredStockValue" xlink:label="loc_us-gaapPreferredStockValue_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStockholdersEquityAbstract_70" xlink:to="loc_us-gaapPreferredStockValue_70" xlink:type="arc" order="31"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockValue" xlink:label="loc_us-gaapCommonStockValue_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStockholdersEquityAbstract_70" xlink:to="loc_us-gaapCommonStockValue_70" xlink:type="arc" order="32"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdditionalPaidInCapital" xlink:label="loc_us-gaapAdditionalPaidInCapital_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStockholdersEquityAbstract_70" xlink:to="loc_us-gaapAdditionalPaidInCapital_70" xlink:type="arc" order="33"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TreasuryStockValue" xlink:label="loc_us-gaapTreasuryStockValue_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStockholdersEquityAbstract_70" xlink:to="loc_us-gaapTreasuryStockValue_70" xlink:type="arc" order="34"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaapAccumulatedOtherComprehensiveIncomeLossNetOfTax_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStockholdersEquityAbstract_70" xlink:to="loc_us-gaapAccumulatedOtherComprehensiveIncomeLossNetOfTax_70" xlink:type="arc" order="35"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="loc_us-gaapRetainedEarningsAccumulatedDeficit_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStockholdersEquityAbstract_70" xlink:to="loc_us-gaapRetainedEarningsAccumulatedDeficit_70" xlink:type="arc" order="36"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="loc_us-gaapStockholdersEquity_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStockholdersEquityAbstract_70" xlink:to="loc_us-gaapStockholdersEquity_70" xlink:type="arc" order="37"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MinorityInterest" xlink:label="loc_us-gaapMinorityInterest_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStockholdersEquityAbstract_70" xlink:to="loc_us-gaapMinorityInterest_70" xlink:type="arc" order="38"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaapStockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStockholdersEquityAbstract_70" xlink:to="loc_us-gaapStockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_70" xlink:type="arc" order="39"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="loc_us-gaapLiabilitiesAndStockholdersEquity_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapLiabilitiesAndStockholdersEquityAbstract_70" xlink:to="loc_us-gaapLiabilitiesAndStockholdersEquity_70" xlink:type="arc" order="40"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/BalanceSheetsParenthetical" xlink:title="00000003 - Statement - Consolidated Balance Sheets (Parenthetical)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaapStatementLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaapStatementTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapStatementTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaapStatementClassOfStockAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapStatementTable" xlink:to="loc_us-gaapStatementClassOfStockAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaapClassOfStockDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapStatementClassOfStockAxis" xlink:to="loc_us-gaapClassOfStockDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaapClassOfStockDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementClassOfStockAxis" xlink:to="loc_us-gaapClassOfStockDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonClassAMember" xlink:label="loc_us-gaapCommonClassAMember_20"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapClassOfStockDomain" xlink:to="loc_us-gaapCommonClassAMember_20" xlink:type="arc" order="21"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonClassBMember" xlink:label="loc_us-gaapCommonClassBMember_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapClassOfStockDomain" xlink:to="loc_us-gaapCommonClassBMember_40" xlink:type="arc" order="41"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent" xlink:label="loc_us-gaapAllowanceForDoubtfulAccountsReceivableCurrent_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapAllowanceForDoubtfulAccountsReceivableCurrent_70" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:label="loc_us-gaapPreferredStockParOrStatedValuePerShare_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapPreferredStockParOrStatedValuePerShare_70" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:label="loc_us-gaapPreferredStockSharesAuthorized_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapPreferredStockSharesAuthorized_70" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PreferredStockSharesIssued" xlink:label="loc_us-gaapPreferredStockSharesIssued_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapPreferredStockSharesIssued_70" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="loc_us-gaapCommonStockParOrStatedValuePerShare_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapCommonStockParOrStatedValuePerShare_70" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="loc_us-gaapCommonStockSharesAuthorized_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapCommonStockSharesAuthorized_70" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockSharesIssued" xlink:label="loc_us-gaapCommonStockSharesIssued_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapCommonStockSharesIssued_70" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="loc_us-gaapCommonStockSharesOutstanding_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapCommonStockSharesOutstanding_70" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TreasuryStockShares" xlink:label="loc_us-gaapTreasuryStockShares_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapTreasuryStockShares_70" xlink:type="arc" order="8"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/StatementsOfOperations" xlink:title="00000004 - Statement - Consolidated Statements of Operations (Unaudited)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/StatementsOfComprehensiveLossIncome" xlink:title="00000005 - Statement - Consolidated Statements of Comprehensive (Loss) Income (Unaudited)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/ConsolidatedStatementsOfEquity" xlink:title="00000006 - Statement - Consolidated Statements of Equity (Unaudited)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaapStatementLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaapStatementTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapStatementTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidatedEntitiesAxis" xlink:label="loc_srtConsolidatedEntitiesAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapStatementTable" xlink:to="loc_srtConsolidatedEntitiesAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidatedEntitiesDomain" xlink:label="loc_srtConsolidatedEntitiesDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srtConsolidatedEntitiesAxis" xlink:to="loc_srtConsolidatedEntitiesDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidatedEntitiesDomain" xlink:label="loc_srtConsolidatedEntitiesDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_srtConsolidatedEntitiesAxis" xlink:to="loc_srtConsolidatedEntitiesDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ParentCompanyMember" xlink:label="loc_srtParentCompanyMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtConsolidatedEntitiesDomain" xlink:to="loc_srtParentCompanyMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaapStatementClassOfStockAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapStatementTable" xlink:to="loc_us-gaapStatementClassOfStockAxis" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaapClassOfStockDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapStatementClassOfStockAxis" xlink:to="loc_us-gaapClassOfStockDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaapClassOfStockDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementClassOfStockAxis" xlink:to="loc_us-gaapClassOfStockDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonClassAMember" xlink:label="loc_us-gaapCommonClassAMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapClassOfStockDomain" xlink:to="loc_us-gaapCommonClassAMember_0" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonClassBMember" xlink:label="loc_us-gaapCommonClassBMember_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapClassOfStockDomain" xlink:to="loc_us-gaapCommonClassBMember_10" xlink:type="arc" order="12"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaapStatementEquityComponentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapStatementTable" xlink:to="loc_us-gaapStatementEquityComponentsAxis" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaapEquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapStatementEquityComponentsAxis" xlink:to="loc_us-gaapEquityComponentDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaapEquityComponentDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementEquityComponentsAxis" xlink:to="loc_us-gaapEquityComponentDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="loc_us-gaapAdditionalPaidInCapitalMember_20"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapEquityComponentDomain" xlink:to="loc_us-gaapAdditionalPaidInCapitalMember_20" xlink:type="arc" order="21"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TreasuryStockMember" xlink:label="loc_us-gaapTreasuryStockMember_30"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapEquityComponentDomain" xlink:to="loc_us-gaapTreasuryStockMember_30" xlink:type="arc" order="31"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="loc_us-gaapAccumulatedOtherComprehensiveIncomeMember_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapEquityComponentDomain" xlink:to="loc_us-gaapAccumulatedOtherComprehensiveIncomeMember_40" xlink:type="arc" order="41"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:label="loc_us-gaapRetainedEarningsMember_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapEquityComponentDomain" xlink:to="loc_us-gaapRetainedEarningsMember_50" xlink:type="arc" order="51"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoncontrollingInterestMember" xlink:label="loc_us-gaapNoncontrollingInterestMember_60"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapEquityComponentDomain" xlink:to="loc_us-gaapNoncontrollingInterestMember_60" xlink:type="arc" order="61"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaapStockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapStockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_90" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharesIssued" xlink:label="loc_us-gaapSharesIssued_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapSharesIssued_90" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" xlink:label="loc_us-gaapStockIssuedDuringPeriodValueStockOptionsExercised_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapStockIssuedDuringPeriodValueStockOptionsExercised_90" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_AdjustmentsFromChangeInRevenueRecognition" xlink:label="loc_idtAdjustmentsFromChangeInRevenueRecognition_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_idtAdjustmentsFromChangeInRevenueRecognition_90" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_CumulativeEffectOnRetainedEarningsNetOfTax" xlink:label="loc_idtCumulativeEffectOnRetainedEarningsNetOfTax_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_idtCumulativeEffectOnRetainedEarningsNetOfTax_90" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestsAdjustedBalance1" xlink:label="loc_idtStockholdersEquityIncludingPortionAttributableToNoncontrollingInterestsAdjustedBalance1_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_idtStockholdersEquityIncludingPortionAttributableToNoncontrollingInterestsAdjustedBalance1_90" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedShareBalance1" xlink:label="loc_idtStockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedShareBalance1_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_idtStockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedShareBalance1_90" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_RepurchaseOfCommonStockUnderStockRepurchaseProgram" xlink:label="loc_idtRepurchaseOfCommonStockUnderStockRepurchaseProgram_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_idtRepurchaseOfCommonStockUnderStockRepurchaseProgram_90" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProceedsFromIssuanceOrSaleOfEquity" xlink:label="loc_us-gaapProceedsFromIssuanceOrSaleOfEquity_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapProceedsFromIssuanceOrSaleOfEquity_90" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_RepurchaseOfRestrictedStock" xlink:label="loc_idtRepurchaseOfRestrictedStock_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_idtRepurchaseOfRestrictedStock_90" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_StockBasedCompensation" xlink:label="loc_idtStockBasedCompensation_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_idtStockBasedCompensation_90" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_StockBasedCompensationShares" xlink:label="loc_idtStockBasedCompensationShares_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_idtStockBasedCompensationShares_90" xlink:type="arc" order="12"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_DistributionToNoncontrollingInterests" xlink:label="loc_idtDistributionToNoncontrollingInterests_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_idtDistributionToNoncontrollingInterests_90" xlink:type="arc" order="13"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaapOtherComprehensiveIncomeLossNetOfTax_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapOtherComprehensiveIncomeLossNetOfTax_90" xlink:type="arc" order="14"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaapProfitLoss_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapProfitLoss_90" xlink:type="arc" order="15"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/StatementsOfCashFlows" xlink:title="00000007 - Statement - Consolidated Statements of Cash Flows (Unaudited)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/BasisOfPresentation" xlink:title="00000008 - Disclosure - Basis of Presentation"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/RevenueRecognition" xlink:title="00000009 - Disclosure - Revenue Recognition"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/Leases" xlink:title="00000010 - Disclosure - Leases"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/CashCashEquivalentsAndRestrictedCashAndCashEquivalents" xlink:title="00000011 - Disclosure - Cash, Cash Equivalents, and Restricted Cash and Cash Equivalents"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/DebtSecurities" xlink:title="00000012 - Disclosure - Debt Securities"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/EquityInvestments" xlink:title="00000013 - Disclosure - Equity Investments"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/FairValueMeasurements" xlink:title="00000014 - Disclosure - Fair Value Measurements"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/AcquisitionOfVersatureCorp." xlink:title="00000015 - Disclosure - Acquisitions"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/OtherOperatingExpenseNet" xlink:title="00000016 - Disclosure - Other Operating Expense, Net"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/Equity" xlink:title="00000017 - Disclosure - Equity"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/EarningsLossPerShare" xlink:title="00000018 - Disclosure - Earnings (Loss) Per Share"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/RevolvingCreditFacility" xlink:title="00000019 - Disclosure - Note Payable and Revolving Credit Loan Payable"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/AccumulatedOtherComprehensiveLoss" xlink:title="00000020 - Disclosure - Accumulated Other Comprehensive Loss"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/BusinessSegmentInformation" xlink:title="00000021 - Disclosure - Business Segment Information"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/CommitmentsAndContingencies" xlink:title="00000022 - Disclosure - Commitments and Contingencies"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/OtherExpenseIncomeNet" xlink:title="00000023 - Disclosure - Other (Expense) Income, Net"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/DefinedContributionPlan" xlink:title="00000024 - Disclosure - Defined Contribution Plan"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/RecentlyIssuedAccountingStandardNotYetAdopted" xlink:title="00000025 - Disclosure - Recently Issued Accounting Standards Not Yet Adopted"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/RevenueRecognitionTables" xlink:title="00000026 - Disclosure - Revenue Recognition (Tables)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/LeasesTables" xlink:title="00000027 - Disclosure - Leases (Tables)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/CashCashEquivalentsAndRestrictedCashAndCashEquivalentsTables" xlink:title="00000028 - Disclosure - Cash, Cash Equivalents, and Restricted Cash and Cash Equivalents (Tables)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/DebtSecuritiesTables" xlink:title="00000029 - Disclosure - Debt Securities (Tables)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/EquityInvestmentsTables" xlink:title="00000030 - Disclosure - Equity Investments (Tables)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/FairValueMeasurementsTables" xlink:title="00000031 - Disclosure - Fair Value Measurements (Tables)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/AcquisitionOfVersatureCorp.Tables" xlink:title="00000032 - Disclosure - Acquisitions (Tables)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/OtherOperatingExpenseNetTables" xlink:title="00000033 - Disclosure - Other Operating Expense, Net (Tables)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/EarningsLossPerShareTables" xlink:title="00000034 - Disclosure - Earnings (Loss) Per Share (Tables)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/AccumulatedOtherComprehensiveLossTables" xlink:title="00000035 - Disclosure - Accumulated Other Comprehensive Loss (Tables)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/BusinessSegmentInformationTables" xlink:title="00000036 - Disclosure - Business Segment Information (Tables)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/OtherExpenseIncomeNetTables" xlink:title="00000037 - Disclosure - Other (Expense) Income, Net (Tables)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/RevenueRecognitionDetails" xlink:title="00000038 - Disclosure - Revenue Recognition (Details)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:label="loc_us-gaapEntityWideInformationRevenueFromExternalCustomerLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:label="loc_us-gaapScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapEntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="loc_us-gaapScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaapStatementBusinessSegmentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:to="loc_us-gaapStatementBusinessSegmentsAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaapSegmentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapStatementBusinessSegmentsAxis" xlink:to="loc_us-gaapSegmentDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaapSegmentDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementBusinessSegmentsAxis" xlink:to="loc_us-gaapSegmentDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_TelecomAndPaymentServiceMember" xlink:label="loc_idtTelecomAndPaymentServiceMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapSegmentDomain" xlink:to="loc_idtTelecomAndPaymentServiceMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_NetTwoPhoneUnifiedCommunicationsAsServiceSegmentMember" xlink:label="loc_idtNetTwoPhoneUnifiedCommunicationsAsServiceSegmentMember_20"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapSegmentDomain" xlink:to="loc_idtNetTwoPhoneUnifiedCommunicationsAsServiceSegmentMember_20" xlink:type="arc" order="21"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductOrServiceAxis" xlink:label="loc_srtProductOrServiceAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:to="loc_srtProductOrServiceAxis" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srtProductsAndServicesDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srtProductOrServiceAxis" xlink:to="loc_srtProductsAndServicesDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srtProductsAndServicesDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_srtProductOrServiceAxis" xlink:to="loc_srtProductsAndServicesDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_BossRevolutionCallingMember" xlink:label="loc_idtBossRevolutionCallingMember_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtProductsAndServicesDomain" xlink:to="loc_idtBossRevolutionCallingMember_40" xlink:type="arc" order="41"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_WholesaleCarrierServicesMember" xlink:label="loc_idtWholesaleCarrierServicesMember_60"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtProductsAndServicesDomain" xlink:to="loc_idtWholesaleCarrierServicesMember_60" xlink:type="arc" order="61"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_MobileTopUpMember" xlink:label="loc_idtMobileTopUpMember_80"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtProductsAndServicesDomain" xlink:to="loc_idtMobileTopUpMember_80" xlink:type="arc" order="81"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_TotalTelecomAndPaymentServicesOtherMember" xlink:label="loc_idtTotalTelecomAndPaymentServicesOtherMember_100"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtProductsAndServicesDomain" xlink:to="loc_idtTotalTelecomAndPaymentServicesOtherMember_100" xlink:type="arc" order="101"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_TotalTelecomAndPaymentServicesGrowthMember" xlink:label="loc_idtTotalTelecomAndPaymentServicesGrowthMember_120"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtProductsAndServicesDomain" xlink:to="loc_idtTotalTelecomAndPaymentServicesGrowthMember_120" xlink:type="arc" order="121"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_NetTwoPhoneUnifiedCommunicationsAsServiceMember" xlink:label="loc_idtNetTwoPhoneUnifiedCommunicationsAsServiceMember_140"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtProductsAndServicesDomain" xlink:to="loc_idtNetTwoPhoneUnifiedCommunicationsAsServiceMember_140" xlink:type="arc" order="141"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_Net2PhonePlatformServicesMember" xlink:label="loc_idtNet2PhonePlatformServicesMember_160"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtProductsAndServicesDomain" xlink:to="loc_idtNet2PhonePlatformServicesMember_160" xlink:type="arc" order="161"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaapRevenues_410"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapEntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="loc_us-gaapRevenues_410" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/RevenueRecognitionDetails1" xlink:title="00000039 - Disclosure - Revenue Recognition (Details 1)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:label="loc_us-gaapEntityWideInformationRevenueFromExternalCustomerLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:label="loc_us-gaapScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapEntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="loc_us-gaapScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaapStatementBusinessSegmentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:to="loc_us-gaapStatementBusinessSegmentsAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaapSegmentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapStatementBusinessSegmentsAxis" xlink:to="loc_us-gaapSegmentDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaapSegmentDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementBusinessSegmentsAxis" xlink:to="loc_us-gaapSegmentDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_TelecomAndPaymentServiceMember" xlink:label="loc_idtTelecomAndPaymentServiceMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapSegmentDomain" xlink:to="loc_idtTelecomAndPaymentServiceMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_NetTwoPhoneUnifiedCommunicationsAsServiceSegmentMember" xlink:label="loc_idtNetTwoPhoneUnifiedCommunicationsAsServiceSegmentMember_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapSegmentDomain" xlink:to="loc_idtNetTwoPhoneUnifiedCommunicationsAsServiceSegmentMember_10" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_StatementGeographicalAxis" xlink:label="loc_srtStatementGeographicalAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:to="loc_srtStatementGeographicalAxis" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_SegmentGeographicalDomain" xlink:label="loc_srtSegmentGeographicalDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srtStatementGeographicalAxis" xlink:to="loc_srtSegmentGeographicalDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_SegmentGeographicalDomain" xlink:label="loc_srtSegmentGeographicalDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_srtStatementGeographicalAxis" xlink:to="loc_srtSegmentGeographicalDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2017/country-2017-01-31.xsd#country_US" xlink:label="loc_countryUS_30"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtSegmentGeographicalDomain" xlink:to="loc_countryUS_30" xlink:type="arc" order="31"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2017/country-2017-01-31.xsd#country_GB" xlink:label="loc_countryGB_60"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtSegmentGeographicalDomain" xlink:to="loc_countryGB_60" xlink:type="arc" order="61"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2017/country-2017-01-31.xsd#country_NL" xlink:label="loc_countryNL_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtSegmentGeographicalDomain" xlink:to="loc_countryNL_90" xlink:type="arc" order="91"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_OtherCountriesMember" xlink:label="loc_idtOtherCountriesMember_120"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtSegmentGeographicalDomain" xlink:to="loc_idtOtherCountriesMember_120" xlink:type="arc" order="121"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GeographicAreasRevenuesFromExternalCustomersAbstract" xlink:label="loc_us-gaapGeographicAreasRevenuesFromExternalCustomersAbstract_610"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapEntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="loc_us-gaapGeographicAreasRevenuesFromExternalCustomersAbstract_610" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_RevenuesFromForeignCustomers" xlink:label="loc_idtRevenuesFromForeignCustomers_610"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapGeographicAreasRevenuesFromExternalCustomersAbstract_610" xlink:to="loc_idtRevenuesFromForeignCustomers_610" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaapRevenues_610"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapGeographicAreasRevenuesFromExternalCustomersAbstract_610" xlink:to="loc_us-gaapRevenues_610" xlink:type="arc" order="2"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/RevenueRecognitionDetails2" xlink:title="00000040 - Disclosure - Revenue Recognition (Details 2)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:label="loc_us-gaapEntityWideInformationRevenueFromExternalCustomerLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:label="loc_us-gaapScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapEntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="loc_us-gaapScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="loc_us-gaapDerivativeInstrumentRiskAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:to="loc_us-gaapDerivativeInstrumentRiskAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaapDerivativeContractTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapDerivativeInstrumentRiskAxis" xlink:to="loc_us-gaapDerivativeContractTypeDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaapDerivativeContractTypeDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapDerivativeInstrumentRiskAxis" xlink:to="loc_us-gaapDerivativeContractTypeDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_ContractLiabilitiesMember" xlink:label="loc_idtContractLiabilitiesMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapDerivativeContractTypeDomain" xlink:to="loc_idtContractLiabilitiesMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized" xlink:label="loc_us-gaapContractWithCustomerLiabilityRevenueRecognized_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapEntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="loc_us-gaapContractWithCustomerLiabilityRevenueRecognized_50" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/RevenueRecognitionDetails3" xlink:title="00000041 - Disclosure - Revenue Recognition (Details 3)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/RevenueRecognitionDetails4" xlink:title="00000042 - Disclosure - Revenue Recognition (Details 4)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/LeasesDetails" xlink:title="00000043 - Disclosure - Leases (Details)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/LeasesDetails1" xlink:title="00000044 - Disclosure - Leases (Details 1)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/LeasesDetails2" xlink:title="00000045 - Disclosure - Leases (Details 2)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/LeasesDetailsTextual" xlink:title="00000046 - Disclosure - Leases (Details Textual)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaapStatementLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaapStatementTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapStatementTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_StatementGeographicalAxis" xlink:label="loc_srtStatementGeographicalAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapStatementTable" xlink:to="loc_srtStatementGeographicalAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_SegmentGeographicalDomain" xlink:label="loc_srtSegmentGeographicalDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srtStatementGeographicalAxis" xlink:to="loc_srtSegmentGeographicalDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_SegmentGeographicalDomain" xlink:label="loc_srtSegmentGeographicalDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_srtStatementGeographicalAxis" xlink:to="loc_srtSegmentGeographicalDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2017/country-2017-01-31.xsd#country_IL" xlink:label="loc_countryIL_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtSegmentGeographicalDomain" xlink:to="loc_countryIL_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_NewarkMember" xlink:label="loc_idtNewarkMember_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtSegmentGeographicalDomain" xlink:to="loc_idtNewarkMember_10" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="loc_us-gaapAdjustmentsForNewAccountingPronouncementsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapStatementTable" xlink:to="loc_us-gaapAdjustmentsForNewAccountingPronouncementsAxis" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaapTypeOfAdoptionMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapAdjustmentsForNewAccountingPronouncementsAxis" xlink:to="loc_us-gaapTypeOfAdoptionMember" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaapTypeOfAdoptionMember_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapAdjustmentsForNewAccountingPronouncementsAxis" xlink:to="loc_us-gaapTypeOfAdoptionMember_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountingStandardsUpdate201602Member" xlink:label="loc_us-gaapAccountingStandardsUpdate201602Member_20"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapTypeOfAdoptionMember" xlink:to="loc_us-gaapAccountingStandardsUpdate201602Member_20" xlink:type="arc" order="21"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaapRelatedPartyTransactionsByRelatedPartyAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapStatementTable" xlink:to="loc_us-gaapRelatedPartyTransactionsByRelatedPartyAxis" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaapRelatedPartyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapRelatedPartyTransactionsByRelatedPartyAxis" xlink:to="loc_us-gaapRelatedPartyDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaapRelatedPartyDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapRelatedPartyTransactionsByRelatedPartyAxis" xlink:to="loc_us-gaapRelatedPartyDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_RafaelHoldingsIncMember" xlink:label="loc_idtRafaelHoldingsIncMember_30"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapRelatedPartyDomain" xlink:to="loc_idtRafaelHoldingsIncMember_30" xlink:type="arc" order="31"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_LeasesTextualAbstract" xlink:label="loc_idtLeasesTextualAbstract_80"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_idtLeasesTextualAbstract_80" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_NewAccountingPronouncementOrChangeInAccountingPrincipleEffectOfAdoptionsQuantification" xlink:label="loc_idtNewAccountingPronouncementOrChangeInAccountingPrincipleEffectOfAdoptionsQuantification_80"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtLeasesTextualAbstract_80" xlink:to="loc_idtNewAccountingPronouncementOrChangeInAccountingPrincipleEffectOfAdoptionsQuantification_80" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LeaseExpirationDate1" xlink:label="loc_us-gaapLeaseExpirationDate1_80"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtLeasesTextualAbstract_80" xlink:to="loc_us-gaapLeaseExpirationDate1_80" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LeaseAndRentalExpense" xlink:label="loc_us-gaapLeaseAndRentalExpense_80"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtLeasesTextualAbstract_80" xlink:to="loc_us-gaapLeaseAndRentalExpense_80" xlink:type="arc" order="3"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/CashCashEquivalentsAndRestrictedCashAndCashEquivalentsDetails" xlink:title="00000047 - Disclosure - Cash, Cash Equivalents, and Restricted Cash and Cash Equivalents (Details)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/CashCashEquivalentsAndRestrictedCashAndCashEquivalentsDetailsTextual" xlink:title="00000048 - Disclosure - Cash, Cash Equivalents, and Restricted Cash and Cash Equivalents (Details Textual)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaapStatementLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaapStatementTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapStatementTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductOrServiceAxis" xlink:label="loc_srtProductOrServiceAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapStatementTable" xlink:to="loc_srtProductOrServiceAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srtProductsAndServicesDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srtProductOrServiceAxis" xlink:to="loc_srtProductsAndServicesDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srtProductsAndServicesDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_srtProductOrServiceAxis" xlink:to="loc_srtProductsAndServicesDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_IDTFinancialServicesLimitedMember" xlink:label="loc_idtIDTFinancialServicesLimitedMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtProductsAndServicesDomain" xlink:to="loc_idtIDTFinancialServicesLimitedMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_CashCashEquivalentsAndRestrictedCashAndCashEquivalentsTextualAbstract" xlink:label="loc_idtCashCashEquivalentsAndRestrictedCashAndCashEquivalentsTextualAbstract_30"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_idtCashCashEquivalentsAndRestrictedCashAndCashEquivalentsTextualAbstract_30" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaapRestrictedCashAndCashEquivalentsAtCarryingValue_30"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtCashCashEquivalentsAndRestrictedCashAndCashEquivalentsTextualAbstract_30" xlink:to="loc_us-gaapRestrictedCashAndCashEquivalentsAtCarryingValue_30" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/DebtSecuritiesDetails" xlink:title="00000049 - Disclosure - Debt Securities (Details)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="loc_us-gaapScheduleOfAvailableForSaleSecuritiesLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesTable" xlink:label="loc_us-gaapScheduleOfAvailableForSaleSecuritiesTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="loc_us-gaapScheduleOfAvailableForSaleSecuritiesTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_MajorTypeOfDebtAndEquitySecuritiesAxis" xlink:label="loc_idtMajorTypeOfDebtAndEquitySecuritiesAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfAvailableForSaleSecuritiesTable" xlink:to="loc_idtMajorTypeOfDebtAndEquitySecuritiesAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_MajorTypeOfDebtAndEquitySecuritiesDomain" xlink:label="loc_idtMajorTypeOfDebtAndEquitySecuritiesDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_idtMajorTypeOfDebtAndEquitySecuritiesAxis" xlink:to="loc_idtMajorTypeOfDebtAndEquitySecuritiesDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_MajorTypeOfDebtAndEquitySecuritiesDomain" xlink:label="loc_idtMajorTypeOfDebtAndEquitySecuritiesDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_idtMajorTypeOfDebtAndEquitySecuritiesAxis" xlink:to="loc_idtMajorTypeOfDebtAndEquitySecuritiesDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CertificatesOfDepositMember" xlink:label="loc_us-gaapCertificatesOfDepositMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtMajorTypeOfDebtAndEquitySecuritiesDomain" xlink:to="loc_us-gaapCertificatesOfDepositMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MunicipalBondsMember" xlink:label="loc_us-gaapMunicipalBondsMember_20"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtMajorTypeOfDebtAndEquitySecuritiesDomain" xlink:to="loc_us-gaapMunicipalBondsMember_20" xlink:type="arc" order="21"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtSecuritiesCurrentAbstract" xlink:label="loc_us-gaapDebtSecuritiesCurrentAbstract_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="loc_us-gaapDebtSecuritiesCurrentAbstract_50" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:label="loc_us-gaapAvailableForSaleDebtSecuritiesAmortizedCostBasis_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapDebtSecuritiesCurrentAbstract_50" xlink:to="loc_us-gaapAvailableForSaleDebtSecuritiesAmortizedCostBasis_50" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" xlink:label="loc_us-gaapAvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapDebtSecuritiesCurrentAbstract_50" xlink:to="loc_us-gaapAvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_50" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" xlink:label="loc_us-gaapAvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapDebtSecuritiesCurrentAbstract_50" xlink:to="loc_us-gaapAvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_50" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:label="loc_us-gaapAvailableForSaleSecuritiesDebtSecurities_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapDebtSecuritiesCurrentAbstract_50" xlink:to="loc_us-gaapAvailableForSaleSecuritiesDebtSecurities_50" xlink:type="arc" order="4"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/DebtSecuritiesDetails1" xlink:title="00000050 - Disclosure - Debt Securities (Details 1)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/DebtSecuritiesDetails2" xlink:title="00000051 - Disclosure - Debt Securities (Details 2)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="loc_us-gaapScheduleOfAvailableForSaleSecuritiesLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesTable" xlink:label="loc_us-gaapScheduleOfAvailableForSaleSecuritiesTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="loc_us-gaapScheduleOfAvailableForSaleSecuritiesTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_MajorTypeOfDebtAndEquitySecuritiesAxis" xlink:label="loc_idtMajorTypeOfDebtAndEquitySecuritiesAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfAvailableForSaleSecuritiesTable" xlink:to="loc_idtMajorTypeOfDebtAndEquitySecuritiesAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_MajorTypeOfDebtAndEquitySecuritiesDomain" xlink:label="loc_idtMajorTypeOfDebtAndEquitySecuritiesDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_idtMajorTypeOfDebtAndEquitySecuritiesAxis" xlink:to="loc_idtMajorTypeOfDebtAndEquitySecuritiesDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_MajorTypeOfDebtAndEquitySecuritiesDomain" xlink:label="loc_idtMajorTypeOfDebtAndEquitySecuritiesDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_idtMajorTypeOfDebtAndEquitySecuritiesAxis" xlink:to="loc_idtMajorTypeOfDebtAndEquitySecuritiesDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CertificatesOfDepositMember" xlink:label="loc_us-gaapCertificatesOfDepositMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtMajorTypeOfDebtAndEquitySecuritiesDomain" xlink:to="loc_us-gaapCertificatesOfDepositMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtSecuritiesCurrentAbstract" xlink:label="loc_us-gaapDebtSecuritiesCurrentAbstract_30"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="loc_us-gaapDebtSecuritiesCurrentAbstract_30" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss" xlink:label="loc_us-gaapAvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss_30"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapDebtSecuritiesCurrentAbstract_30" xlink:to="loc_us-gaapAvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss_30" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue" xlink:label="loc_us-gaapAvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue_30"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapDebtSecuritiesCurrentAbstract_30" xlink:to="loc_us-gaapAvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue_30" xlink:type="arc" order="2"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/DebtSecuritiesDetailsTextual" xlink:title="00000052 - Disclosure - Debt Securities (Details Textual)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/EquityInvestmentsDetails" xlink:title="00000053 - Disclosure - Equity Investments (Details)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueLineItems" xlink:label="loc_us-gaapEquitySecuritiesWithoutReadilyDeterminableFairValueLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueTable" xlink:label="loc_us-gaapEquitySecuritiesWithoutReadilyDeterminableFairValueTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapEquitySecuritiesWithoutReadilyDeterminableFairValueLineItems" xlink:to="loc_us-gaapEquitySecuritiesWithoutReadilyDeterminableFairValueTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_deiLegalEntityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapEquitySecuritiesWithoutReadilyDeterminableFairValueTable" xlink:to="loc_deiLegalEntityAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:label="loc_deiEntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_deiLegalEntityAxis" xlink:to="loc_deiEntityDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:label="loc_deiEntityDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_deiLegalEntityAxis" xlink:to="loc_deiEntityDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_ZedgeIncMember" xlink:label="loc_idtZedgeIncMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_deiEntityDomain" xlink:to="loc_idtZedgeIncMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_RafaelSpinOffMember" xlink:label="loc_idtRafaelSpinOffMember_20"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_deiEntityDomain" xlink:to="loc_idtRafaelSpinOffMember_20" xlink:type="arc" order="21"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaapStatementClassOfStockAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapEquitySecuritiesWithoutReadilyDeterminableFairValueTable" xlink:to="loc_us-gaapStatementClassOfStockAxis" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaapClassOfStockDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapStatementClassOfStockAxis" xlink:to="loc_us-gaapClassOfStockDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaapClassOfStockDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementClassOfStockAxis" xlink:to="loc_us-gaapClassOfStockDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonClassBMember" xlink:label="loc_us-gaapCommonClassBMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapClassOfStockDomain" xlink:to="loc_us-gaapCommonClassBMember_0" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SeriesBPreferredStockMember" xlink:label="loc_us-gaapSeriesBPreferredStockMember_80"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapClassOfStockDomain" xlink:to="loc_us-gaapSeriesBPreferredStockMember_80" xlink:type="arc" order="81"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InvestmentTypeAxis" xlink:label="loc_us-gaapInvestmentTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapEquitySecuritiesWithoutReadilyDeterminableFairValueTable" xlink:to="loc_us-gaapInvestmentTypeAxis" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaapInvestmentTypeCategorizationMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapInvestmentTypeAxis" xlink:to="loc_us-gaapInvestmentTypeCategorizationMember" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaapInvestmentTypeCategorizationMember_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapInvestmentTypeAxis" xlink:to="loc_us-gaapInvestmentTypeCategorizationMember_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MutualFundMember" xlink:label="loc_us-gaapMutualFundMember_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapInvestmentTypeCategorizationMember" xlink:to="loc_us-gaapMutualFundMember_40" xlink:type="arc" order="41"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgeFundsMember" xlink:label="loc_us-gaapHedgeFundsMember_100"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapInvestmentTypeCategorizationMember" xlink:to="loc_us-gaapHedgeFundsMember_100" xlink:type="arc" order="101"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationAxis" xlink:label="loc_us-gaapOtherComprehensiveIncomeLocationAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapEquitySecuritiesWithoutReadilyDeterminableFairValueTable" xlink:to="loc_us-gaapOtherComprehensiveIncomeLocationAxis" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain" xlink:label="loc_us-gaapOtherComprehensiveIncomeLocationDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapOtherComprehensiveIncomeLocationAxis" xlink:to="loc_us-gaapOtherComprehensiveIncomeLocationDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain" xlink:label="loc_us-gaapOtherComprehensiveIncomeLocationDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapOtherComprehensiveIncomeLocationAxis" xlink:to="loc_us-gaapOtherComprehensiveIncomeLocationDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherInvestmentsMember" xlink:label="loc_us-gaapOtherInvestmentsMember_120"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapOtherComprehensiveIncomeLocationDomain" xlink:to="loc_us-gaapOtherInvestmentsMember_120" xlink:type="arc" order="121"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherShortTermInvestments" xlink:label="loc_us-gaapOtherShortTermInvestments_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapEquitySecuritiesWithoutReadilyDeterminableFairValueLineItems" xlink:to="loc_us-gaapOtherShortTermInvestments_150" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermInvestments" xlink:label="loc_us-gaapLongTermInvestments_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapEquitySecuritiesWithoutReadilyDeterminableFairValueLineItems" xlink:to="loc_us-gaapLongTermInvestments_150" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/EquityInvestmentsDetails1" xlink:title="00000054 - Disclosure - Equity Investments (Details 1)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/EquityInvestmentsDetails2" xlink:title="00000055 - Disclosure - Equity Investments (Details 2)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/EquityInvestmentsDetailsTextual" xlink:title="00000056 - Disclosure - Equity Investments (Details Textual)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="loc_us-gaapScheduleOfAvailableForSaleSecuritiesLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesTable" xlink:label="loc_us-gaapScheduleOfAvailableForSaleSecuritiesTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="loc_us-gaapScheduleOfAvailableForSaleSecuritiesTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaapStatementClassOfStockAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfAvailableForSaleSecuritiesTable" xlink:to="loc_us-gaapStatementClassOfStockAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaapClassOfStockDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapStatementClassOfStockAxis" xlink:to="loc_us-gaapClassOfStockDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaapClassOfStockDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementClassOfStockAxis" xlink:to="loc_us-gaapClassOfStockDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonClassBMember" xlink:label="loc_us-gaapCommonClassBMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapClassOfStockDomain" xlink:to="loc_us-gaapCommonClassBMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_VisaSeriesCConvertibleParticipatingPreferredStockMember" xlink:label="loc_idtVisaSeriesCConvertibleParticipatingPreferredStockMember_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapClassOfStockDomain" xlink:to="loc_idtVisaSeriesCConvertibleParticipatingPreferredStockMember_40" xlink:type="arc" order="41"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_deiLegalEntityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfAvailableForSaleSecuritiesTable" xlink:to="loc_deiLegalEntityAxis" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:label="loc_deiEntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_deiLegalEntityAxis" xlink:to="loc_deiEntityDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:label="loc_deiEntityDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_deiLegalEntityAxis" xlink:to="loc_deiEntityDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_ZedgeIncMember" xlink:label="loc_idtZedgeIncMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_deiEntityDomain" xlink:to="loc_idtZedgeIncMember_0" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_RafaelHoldingsIncMember" xlink:label="loc_idtRafaelHoldingsIncMember_20"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_deiEntityDomain" xlink:to="loc_idtRafaelHoldingsIncMember_20" xlink:type="arc" order="22"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_EquityInvestmentsTextualAbstract" xlink:label="loc_idtEquityInvestmentsTextualAbstract_120"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="loc_idtEquityInvestmentsTextualAbstract_120" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_NewAccountingPronouncementOrChangeInAccountingPrincipleCumulativeEffectOfChangeOnEquityOrNetAssets2" xlink:label="loc_idtNewAccountingPronouncementOrChangeInAccountingPrincipleCumulativeEffectOfChangeOnEquityOrNetAssets2_120"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityInvestmentsTextualAbstract_120" xlink:to="loc_idtNewAccountingPronouncementOrChangeInAccountingPrincipleCumulativeEffectOfChangeOnEquityOrNetAssets2_120" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InvestmentOwnedBalanceShares" xlink:label="loc_us-gaapInvestmentOwnedBalanceShares_120"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityInvestmentsTextualAbstract_120" xlink:to="loc_us-gaapInvestmentOwnedBalanceShares_120" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardDownwardPriceAdjustmentAnnualAmount" xlink:label="loc_idtEquitySecuritiesWithoutReadilyDeterminableFairValueUpwardDownwardPriceAdjustmentAnnualAmount_120"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityInvestmentsTextualAbstract_120" xlink:to="loc_idtEquitySecuritiesWithoutReadilyDeterminableFairValueUpwardDownwardPriceAdjustmentAnnualAmount_120" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConvertiblePreferredStockSharesIssuedUponConversion" xlink:label="loc_us-gaapConvertiblePreferredStockSharesIssuedUponConversion_120"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityInvestmentsTextualAbstract_120" xlink:to="loc_us-gaapConvertiblePreferredStockSharesIssuedUponConversion_120" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_NumberOfRelatedPartySharesReceivedInConnectionWithRestrictedStock" xlink:label="loc_idtNumberOfRelatedPartySharesReceivedInConnectionWithRestrictedStock_120"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityInvestmentsTextualAbstract_120" xlink:to="loc_idtNumberOfRelatedPartySharesReceivedInConnectionWithRestrictedStock_120" xlink:type="arc" order="5"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/FairValueMeasurementsDetails" xlink:title="00000057 - Disclosure - Fair Value Measurements (Details)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaapFairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaapFairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapFairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="loc_us-gaapFairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="loc_us-gaapFairValueByMeasurementFrequencyAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapFairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="loc_us-gaapFairValueByMeasurementFrequencyAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaapFairValueMeasurementFrequencyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapFairValueByMeasurementFrequencyAxis" xlink:to="loc_us-gaapFairValueMeasurementFrequencyDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaapFairValueMeasurementFrequencyDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapFairValueByMeasurementFrequencyAxis" xlink:to="loc_us-gaapFairValueMeasurementFrequencyDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:label="loc_us-gaapFairValueMeasurementsRecurringMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueMeasurementFrequencyDomain" xlink:to="loc_us-gaapFairValueMeasurementsRecurringMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaapFairValueByFairValueHierarchyLevelAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapFairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="loc_us-gaapFairValueByFairValueHierarchyLevelAxis" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaapFairValueMeasurementsFairValueHierarchyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapFairValueByFairValueHierarchyLevelAxis" xlink:to="loc_us-gaapFairValueMeasurementsFairValueHierarchyDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaapFairValueMeasurementsFairValueHierarchyDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapFairValueByFairValueHierarchyLevelAxis" xlink:to="loc_us-gaapFairValueMeasurementsFairValueHierarchyDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="loc_us-gaapFairValueInputsLevel1Member_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueMeasurementsFairValueHierarchyDomain" xlink:to="loc_us-gaapFairValueInputsLevel1Member_0" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="loc_us-gaapFairValueInputsLevel2Member_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueMeasurementsFairValueHierarchyDomain" xlink:to="loc_us-gaapFairValueInputsLevel2Member_10" xlink:type="arc" order="12"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaapFairValueInputsLevel3Member_20"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueMeasurementsFairValueHierarchyDomain" xlink:to="loc_us-gaapFairValueInputsLevel3Member_20" xlink:type="arc" order="22"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:label="loc_us-gaapAvailableForSaleSecuritiesDebtSecurities_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="loc_us-gaapAvailableForSaleSecuritiesDebtSecurities_90" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_EquityInvestmentsCurrentAsset" xlink:label="loc_idtEquityInvestmentsCurrentAsset_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="loc_idtEquityInvestmentsCurrentAsset_90" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_EquityInvestmentsNoncurrentAssets" xlink:label="loc_idtEquityInvestmentsNoncurrentAssets_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="loc_idtEquityInvestmentsNoncurrentAssets_90" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InvestmentsFairValueDisclosure" xlink:label="loc_us-gaapInvestmentsFairValueDisclosure_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="loc_us-gaapInvestmentsFairValueDisclosure_90" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_ContingentConsiderationIncludedInOtherNoncurrentLiabilities" xlink:label="loc_idtContingentConsiderationIncludedInOtherNoncurrentLiabilities_90"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="loc_idtContingentConsiderationIncludedInOtherNoncurrentLiabilities_90" xlink:type="arc" order="4"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/FairValueMeasurementsDetails1" xlink:title="00000058 - Disclosure - Fair Value Measurements (Details 1)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:label="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:label="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaapFairValueByFairValueHierarchyLevelAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:to="loc_us-gaapFairValueByFairValueHierarchyLevelAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaapFairValueMeasurementsFairValueHierarchyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapFairValueByFairValueHierarchyLevelAxis" xlink:to="loc_us-gaapFairValueMeasurementsFairValueHierarchyDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaapFairValueMeasurementsFairValueHierarchyDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapFairValueByFairValueHierarchyLevelAxis" xlink:to="loc_us-gaapFairValueMeasurementsFairValueHierarchyDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaapFairValueInputsLevel3Member_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueMeasurementsFairValueHierarchyDomain" xlink:to="loc_us-gaapFairValueInputsLevel3Member_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" xlink:label="loc_us-gaapFairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="loc_us-gaapFairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_50" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevelThreeFromAdoptionOfAccountingChange" xlink:label="loc_idtFairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevelThreeFromAdoptionOfAccountingChange_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="loc_idtFairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevelThreeFromAdoptionOfAccountingChange_50" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1" xlink:label="loc_us-gaapFairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="loc_us-gaapFairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_50" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_AmountOfChangeInUnrealizedGainsOrLossesIncludedInEarningsForAssetsHeldAtEndOfPeriod" xlink:label="loc_idtAmountOfChangeInUnrealizedGainsOrLossesIncludedInEarningsForAssetsHeldAtEndOfPeriod_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="loc_idtAmountOfChangeInUnrealizedGainsOrLossesIncludedInEarningsForAssetsHeldAtEndOfPeriod_50" xlink:type="arc" order="4"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/FairValueMeasurementsDetails2" xlink:title="00000059 - Disclosure - Fair Value Measurements (Details 2)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:label="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:label="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaapFairValueByFairValueHierarchyLevelAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:to="loc_us-gaapFairValueByFairValueHierarchyLevelAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaapFairValueMeasurementsFairValueHierarchyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapFairValueByFairValueHierarchyLevelAxis" xlink:to="loc_us-gaapFairValueMeasurementsFairValueHierarchyDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaapFairValueMeasurementsFairValueHierarchyDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapFairValueByFairValueHierarchyLevelAxis" xlink:to="loc_us-gaapFairValueMeasurementsFairValueHierarchyDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaapFairValueInputsLevel3Member_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueMeasurementsFairValueHierarchyDomain" xlink:to="loc_us-gaapFairValueInputsLevel3Member_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue" xlink:label="loc_us-gaapFairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="loc_us-gaapFairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_50" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesTransfersIntoLevelThreeFromAcquisition" xlink:label="loc_idtFairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesTransfersIntoLevelThreeFromAcquisition_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="loc_idtFairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesTransfersIntoLevelThreeFromAcquisition_50" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome" xlink:label="loc_us-gaapFairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="loc_us-gaapFairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome_50" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_AmountOfChangeInUnrealizedGainsOrLossesIncludedInEarningsForLiabilitiesHeldAtEndOfPeriod" xlink:label="loc_idtAmountOfChangeInUnrealizedGainsOrLossesIncludedInEarningsForLiabilitiesHeldAtEndOfPeriod_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapFairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="loc_idtAmountOfChangeInUnrealizedGainsOrLossesIncludedInEarningsForLiabilitiesHeldAtEndOfPeriod_50" xlink:type="arc" order="4"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/FairValueMeasurementsDetailsTextual" xlink:title="00000060 - Disclosure - Fair Value Measurements (Details Textual)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/AcquisitionsDetails" xlink:title="00000061 - Disclosure - Acquisitions (Details)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/AcquisitionsDetails1" xlink:title="00000062 - Disclosure - Acquisitions (Details 1)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/AcquisitionsDetailsTextual" xlink:title="00000063 - Disclosure - Acquisitions (Details Textual)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaapStatementLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaapStatementTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapStatementTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaapBusinessAcquisitionAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapStatementTable" xlink:to="loc_us-gaapBusinessAcquisitionAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaapBusinessAcquisitionAcquireeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapBusinessAcquisitionAxis" xlink:to="loc_us-gaapBusinessAcquisitionAcquireeDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaapBusinessAcquisitionAcquireeDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapBusinessAcquisitionAxis" xlink:to="loc_us-gaapBusinessAcquisitionAcquireeDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_VersatureCorpMember" xlink:label="loc_idtVersatureCorpMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapBusinessAcquisitionAcquireeDomain" xlink:to="loc_idtVersatureCorpMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_RingsouthEuropaSLMember" xlink:label="loc_idtRingsouthEuropaSLMember_20"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapBusinessAcquisitionAcquireeDomain" xlink:to="loc_idtRingsouthEuropaSLMember_20" xlink:type="arc" order="21"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_AcquisitionOfVersatureCorpTextualAbstract" xlink:label="loc_idtAcquisitionOfVersatureCorpTextualAbstract_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_idtAcquisitionOfVersatureCorpTextualAbstract_50" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross" xlink:label="loc_us-gaapPaymentsToAcquireBusinessesGross_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtAcquisitionOfVersatureCorpTextualAbstract_50" xlink:to="loc_us-gaapPaymentsToAcquireBusinessesGross_50" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireePercentage" xlink:label="loc_us-gaapBusinessCombinationStepAcquisitionEquityInterestInAcquireePercentage_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtAcquisitionOfVersatureCorpTextualAbstract_50" xlink:to="loc_us-gaapBusinessCombinationStepAcquisitionEquityInterestInAcquireePercentage_50" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsDescription" xlink:label="loc_us-gaapBusinessCombinationContingentConsiderationArrangementsDescription_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtAcquisitionOfVersatureCorpTextualAbstract_50" xlink:to="loc_us-gaapBusinessCombinationContingentConsiderationArrangementsDescription_50" xlink:type="arc" order="3"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/OtherOperatingExpenseNetDetails" xlink:title="00000064 - Disclosure - Other Operating Expense, Net (Details)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/OtherOperatingExpenseNetDetails1" xlink:title="00000065 - Disclosure - Other Operating Expense, Net (Details 1)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaapStatementLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaapStatementTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapStatementTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RestatementAxis" xlink:label="loc_srtRestatementAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapStatementTable" xlink:to="loc_srtRestatementAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RestatementDomain" xlink:label="loc_srtRestatementDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srtRestatementAxis" xlink:to="loc_srtRestatementDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RestatementDomain" xlink:label="loc_srtRestatementDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_srtRestatementAxis" xlink:to="loc_srtRestatementDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ScenarioPreviouslyReportedMember" xlink:label="loc_srtScenarioPreviouslyReportedMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtRestatementDomain" xlink:to="loc_srtScenarioPreviouslyReportedMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RestatementAdjustmentMember" xlink:label="loc_srtRestatementAdjustmentMember_20"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtRestatementDomain" xlink:to="loc_srtRestatementAdjustmentMember_20" xlink:type="arc" order="21"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementByRestatementPeriodAndAmountAxis" xlink:label="loc_us-gaapErrorCorrectionsAndPriorPeriodAdjustmentsRestatementByRestatementPeriodAndAmountAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapStatementTable" xlink:to="loc_us-gaapErrorCorrectionsAndPriorPeriodAdjustmentsRestatementByRestatementPeriodAndAmountAxis" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsForErrorCorrectionDomain" xlink:label="loc_us-gaapAdjustmentsForErrorCorrectionDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapErrorCorrectionsAndPriorPeriodAdjustmentsRestatementByRestatementPeriodAndAmountAxis" xlink:to="loc_us-gaapAdjustmentsForErrorCorrectionDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsForErrorCorrectionDomain" xlink:label="loc_us-gaapAdjustmentsForErrorCorrectionDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapErrorCorrectionsAndPriorPeriodAdjustmentsRestatementByRestatementPeriodAndAmountAxis" xlink:to="loc_us-gaapAdjustmentsForErrorCorrectionDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_ErrorCorrectionMember" xlink:label="loc_idtErrorCorrectionMember_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAdjustmentsForErrorCorrectionDomain" xlink:to="loc_idtErrorCorrectionMember_10" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems" xlink:label="loc_us-gaapErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapStatementLineItems" xlink:to="loc_us-gaapErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_70" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherOperatingIncomeExpenseNet" xlink:label="loc_us-gaapOtherOperatingIncomeExpenseNet_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_70" xlink:to="loc_us-gaapOtherOperatingIncomeExpenseNet_70" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="loc_us-gaapIncomeTaxExpenseBenefit_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_70" xlink:to="loc_us-gaapIncomeTaxExpenseBenefit_70" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaapProfitLoss_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_70" xlink:to="loc_us-gaapProfitLoss_70" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaapNetIncomeLoss_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_70" xlink:to="loc_us-gaapNetIncomeLoss_70" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareAbstract" xlink:label="loc_us-gaapEarningsPerShareAbstract_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_70" xlink:to="loc_us-gaapEarningsPerShareAbstract_70" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasic" xlink:label="loc_us-gaapEarningsPerShareBasic_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_70" xlink:to="loc_us-gaapEarningsPerShareBasic_70" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="loc_us-gaapEarningsPerShareDiluted_70"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_70" xlink:to="loc_us-gaapEarningsPerShareDiluted_70" xlink:type="arc" order="7"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/OtherOperatingExpenseNetDetailsTextual" xlink:title="00000066 - Disclosure - Other Operating Expense, Net (Details Textual)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaapRelatedPartyTransactionLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaapScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapRelatedPartyTransactionLineItems" xlink:to="loc_us-gaapScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaapRelatedPartyTransactionsByRelatedPartyAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="loc_us-gaapRelatedPartyTransactionsByRelatedPartyAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaapRelatedPartyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapRelatedPartyTransactionsByRelatedPartyAxis" xlink:to="loc_us-gaapRelatedPartyDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaapRelatedPartyDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapRelatedPartyTransactionsByRelatedPartyAxis" xlink:to="loc_us-gaapRelatedPartyDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_StraightPathMember" xlink:label="loc_idtStraightPathMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapRelatedPartyDomain" xlink:to="loc_idtStraightPathMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_OtherOperatingExpensesGainsNetTextualAbstract" xlink:label="loc_idtOtherOperatingExpensesGainsNetTextualAbstract_60"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapRelatedPartyTransactionLineItems" xlink:to="loc_idtOtherOperatingExpensesGainsNetTextualAbstract_60" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_UnusualOrInfrequentItemInsuranceProceeds" xlink:label="loc_us-gaapUnusualOrInfrequentItemInsuranceProceeds_60"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtOtherOperatingExpensesGainsNetTextualAbstract_60" xlink:to="loc_us-gaapUnusualOrInfrequentItemInsuranceProceeds_60" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LegalFees" xlink:label="loc_us-gaapLegalFees_60"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtOtherOperatingExpensesGainsNetTextualAbstract_60" xlink:to="loc_us-gaapLegalFees_60" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrentAndNoncurrent" xlink:label="loc_us-gaapAccrualForTaxesOtherThanIncomeTaxesCurrentAndNoncurrent_60"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtOtherOperatingExpensesGainsNetTextualAbstract_60" xlink:to="loc_us-gaapAccrualForTaxesOtherThanIncomeTaxesCurrentAndNoncurrent_60" xlink:type="arc" order="3"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/EquityDetails" xlink:title="00000067 - Disclosure - Equity (Details)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockLineItems" xlink:label="loc_us-gaapClassOfStockLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="loc_us-gaapScheduleOfStockByClassTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapClassOfStockLineItems" xlink:to="loc_us-gaapScheduleOfStockByClassTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaapStatementClassOfStockAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfStockByClassTable" xlink:to="loc_us-gaapStatementClassOfStockAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaapClassOfStockDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapStatementClassOfStockAxis" xlink:to="loc_us-gaapClassOfStockDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaapClassOfStockDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementClassOfStockAxis" xlink:to="loc_us-gaapClassOfStockDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonClassBMember" xlink:label="loc_us-gaapCommonClassBMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapClassOfStockDomain" xlink:to="loc_us-gaapCommonClassBMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaapRelatedPartyTransactionsByRelatedPartyAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfStockByClassTable" xlink:to="loc_us-gaapRelatedPartyTransactionsByRelatedPartyAxis" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaapRelatedPartyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapRelatedPartyTransactionsByRelatedPartyAxis" xlink:to="loc_us-gaapRelatedPartyDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaapRelatedPartyDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapRelatedPartyTransactionsByRelatedPartyAxis" xlink:to="loc_us-gaapRelatedPartyDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_EmployessMember" xlink:label="loc_idtEmployessMember_30"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapRelatedPartyDomain" xlink:to="loc_idtEmployessMember_30" xlink:type="arc" order="32"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaapAwardTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfStockByClassTable" xlink:to="loc_us-gaapAwardTypeAxis" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaapShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapAwardTypeAxis" xlink:to="loc_us-gaapShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaapShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapAwardTypeAxis" xlink:to="loc_us-gaapShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_DeferredStockUnitsMember" xlink:label="loc_idtDeferredStockUnitsMember_60"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_idtDeferredStockUnitsMember_60" xlink:type="arc" order="62"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareRepurchaseProgramAxis" xlink:label="loc_us-gaapShareRepurchaseProgramAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfStockByClassTable" xlink:to="loc_us-gaapShareRepurchaseProgramAxis" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain" xlink:label="loc_us-gaapShareRepurchaseProgramDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapShareRepurchaseProgramAxis" xlink:to="loc_us-gaapShareRepurchaseProgramDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain" xlink:label="loc_us-gaapShareRepurchaseProgramDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapShareRepurchaseProgramAxis" xlink:to="loc_us-gaapShareRepurchaseProgramDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_TwoThousandFifteenStockOptionAndIncentivePlanMember" xlink:label="loc_idtTwoThousandFifteenStockOptionAndIncentivePlanMember_80"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapShareRepurchaseProgramDomain" xlink:to="loc_idtTwoThousandFifteenStockOptionAndIncentivePlanMember_80" xlink:type="arc" order="82"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_TitleOfIndividualAxis" xlink:label="loc_srtTitleOfIndividualAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfStockByClassTable" xlink:to="loc_srtTitleOfIndividualAxis" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="loc_srtTitleOfIndividualWithRelationshipToEntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srtTitleOfIndividualAxis" xlink:to="loc_srtTitleOfIndividualWithRelationshipToEntityDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="loc_srtTitleOfIndividualWithRelationshipToEntityDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_srtTitleOfIndividualAxis" xlink:to="loc_srtTitleOfIndividualWithRelationshipToEntityDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_JonasMember" xlink:label="loc_idtJonasMember_100"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtTitleOfIndividualWithRelationshipToEntityDomain" xlink:to="loc_idtJonasMember_100" xlink:type="arc" order="102"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_EquityTextualAbstract" xlink:label="loc_idtEquityTextualAbstract_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapClassOfStockLineItems" xlink:to="loc_idtEquityTextualAbstract_150" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased" xlink:label="loc_us-gaapStockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityTextualAbstract_150" xlink:to="loc_us-gaapStockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased_150" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TreasuryStockSharesAcquired" xlink:label="loc_us-gaapTreasuryStockSharesAcquired_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityTextualAbstract_150" xlink:to="loc_us-gaapTreasuryStockSharesAcquired_150" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:label="loc_us-gaapTreasuryStockValueAcquiredCostMethod_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityTextualAbstract_150" xlink:to="loc_us-gaapTreasuryStockValueAcquiredCostMethod_150" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased" xlink:label="loc_us-gaapStockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityTextualAbstract_150" xlink:to="loc_us-gaapStockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased_150" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized" xlink:label="loc_us-gaapShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityTextualAbstract_150" xlink:to="loc_us-gaapShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_150" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" xlink:label="loc_us-gaapStockIssuedDuringPeriodValueStockOptionsExercised_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityTextualAbstract_150" xlink:to="loc_us-gaapStockIssuedDuringPeriodValueStockOptionsExercised_150" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="loc_us-gaapStockIssuedDuringPeriodSharesStockOptionsExercised_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityTextualAbstract_150" xlink:to="loc_us-gaapStockIssuedDuringPeriodSharesStockOptionsExercised_150" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction" xlink:label="loc_us-gaapSaleOfStockNumberOfSharesIssuedInTransaction_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityTextualAbstract_150" xlink:to="loc_us-gaapSaleOfStockNumberOfSharesIssuedInTransaction_150" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="loc_us-gaapProceedsFromIssuanceOfCommonStock_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityTextualAbstract_150" xlink:to="loc_us-gaapProceedsFromIssuanceOfCommonStock_150" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SaleOfStockPricePerShare" xlink:label="loc_us-gaapSaleOfStockPricePerShare_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityTextualAbstract_150" xlink:to="loc_us-gaapSaleOfStockPricePerShare_150" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_ReductionToProceedsFromIssuanceOfCommonStock" xlink:label="loc_idtReductionToProceedsFromIssuanceOfCommonStock_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityTextualAbstract_150" xlink:to="loc_idtReductionToProceedsFromIssuanceOfCommonStock_150" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:label="loc_us-gaapShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityTextualAbstract_150" xlink:to="loc_us-gaapShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_150" xlink:type="arc" order="12"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestingDeferredInPeriod" xlink:label="loc_idtShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestingDeferredInPeriod_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityTextualAbstract_150" xlink:to="loc_idtShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestingDeferredInPeriod_150" xlink:type="arc" order="13"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted" xlink:label="loc_us-gaapShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityTextualAbstract_150" xlink:to="loc_us-gaapShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_150" xlink:type="arc" order="14"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="loc_us-gaapShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_150"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtEquityTextualAbstract_150" xlink:to="loc_us-gaapShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_150" xlink:type="arc" order="15"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/EarningsLossPerShareDetails" xlink:title="00000068 - Disclosure - Earnings (Loss) Per Share (Details)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/EarningsLossPerShareDetails1" xlink:title="00000069 - Disclosure - Earnings (Loss) Per Share (Details 1)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:label="loc_us-gaapAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:label="loc_us-gaapScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:to="loc_us-gaapScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:label="loc_us-gaapAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:to="loc_us-gaapAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaapAntidilutiveSecuritiesNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:to="loc_us-gaapAntidilutiveSecuritiesNameDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaapAntidilutiveSecuritiesNameDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:to="loc_us-gaapAntidilutiveSecuritiesNameDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaapEmployeeStockOptionMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAntidilutiveSecuritiesNameDomain" xlink:to="loc_us-gaapEmployeeStockOptionMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_NonvestedRestrictedClassBCommonStockMember" xlink:label="loc_idtNonvestedRestrictedClassBCommonStockMember_20"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAntidilutiveSecuritiesNameDomain" xlink:to="loc_idtNonvestedRestrictedClassBCommonStockMember_20" xlink:type="arc" order="21"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareDilutedOtherDisclosuresAbstract" xlink:label="loc_us-gaapEarningsPerShareDilutedOtherDisclosuresAbstract_130"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:to="loc_us-gaapEarningsPerShareDilutedOtherDisclosuresAbstract_130" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:label="loc_us-gaapAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_130"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapEarningsPerShareDilutedOtherDisclosuresAbstract_130" xlink:to="loc_us-gaapAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_130" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/NotePayableAndRevolvingCreditLoanPayableDetails" xlink:title="00000070 - Disclosure - Note Payable and Revolving Credit Loan Payable (Details)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/AccumulatedOtherComprehensiveLossDetails" xlink:title="00000071 - Disclosure - Accumulated Other Comprehensive Loss (Details)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems" xlink:label="loc_us-gaapAccumulatedOtherComprehensiveIncomeLossLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable" xlink:label="loc_us-gaapAccumulatedOtherComprehensiveIncomeLossTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapAccumulatedOtherComprehensiveIncomeLossLineItems" xlink:to="loc_us-gaapAccumulatedOtherComprehensiveIncomeLossTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaapStatementEquityComponentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapAccumulatedOtherComprehensiveIncomeLossTable" xlink:to="loc_us-gaapStatementEquityComponentsAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaapEquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapStatementEquityComponentsAxis" xlink:to="loc_us-gaapEquityComponentDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaapEquityComponentDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementEquityComponentsAxis" xlink:to="loc_us-gaapEquityComponentDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember" xlink:label="loc_us-gaapAccumulatedNetUnrealizedInvestmentGainLossMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapEquityComponentDomain" xlink:to="loc_us-gaapAccumulatedNetUnrealizedInvestmentGainLossMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedTranslationAdjustmentMember" xlink:label="loc_us-gaapAccumulatedTranslationAdjustmentMember_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapEquityComponentDomain" xlink:to="loc_us-gaapAccumulatedTranslationAdjustmentMember_10" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_AccumulatedOtherComprehensiveMember" xlink:label="loc_idtAccumulatedOtherComprehensiveMember_20"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapEquityComponentDomain" xlink:to="loc_idtAccumulatedOtherComprehensiveMember_20" xlink:type="arc" order="21"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaapIncomeStatementLocationAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapAccumulatedOtherComprehensiveIncomeLossTable" xlink:to="loc_us-gaapIncomeStatementLocationAxis" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaapIncomeStatementLocationDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapIncomeStatementLocationAxis" xlink:to="loc_us-gaapIncomeStatementLocationDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaapIncomeStatementLocationDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapIncomeStatementLocationAxis" xlink:to="loc_us-gaapIncomeStatementLocationDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_ScheduleOfAccumulatedBalancesForEachClassificationOfOtherComprehensiveIncomeLossAbstract" xlink:label="loc_idtScheduleOfAccumulatedBalancesForEachClassificationOfOtherComprehensiveIncomeLossAbstract_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapAccumulatedOtherComprehensiveIncomeLossLineItems" xlink:to="loc_idtScheduleOfAccumulatedBalancesForEachClassificationOfOtherComprehensiveIncomeLossAbstract_40" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaapAccumulatedOtherComprehensiveIncomeLossNetOfTax_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtScheduleOfAccumulatedBalancesForEachClassificationOfOtherComprehensiveIncomeLossAbstract_40" xlink:to="loc_us-gaapAccumulatedOtherComprehensiveIncomeLossNetOfTax_40" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaapOtherComprehensiveIncomeLossNetOfTax_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtScheduleOfAccumulatedBalancesForEachClassificationOfOtherComprehensiveIncomeLossAbstract_40" xlink:to="loc_us-gaapOtherComprehensiveIncomeLossNetOfTax_40" xlink:type="arc" order="2"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/BusinessSegmentInformationDetails" xlink:title="00000072 - Disclosure - Business Segment Information (Details)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="loc_us-gaapSegmentReportingInformationLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="loc_us-gaapScheduleOfSegmentReportingInformationBySegmentTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapSegmentReportingInformationLineItems" xlink:to="loc_us-gaapScheduleOfSegmentReportingInformationBySegmentTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsAxis" xlink:label="loc_srtConsolidationItemsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfSegmentReportingInformationBySegmentTable" xlink:to="loc_srtConsolidationItemsAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srtConsolidationItemsDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srtConsolidationItemsAxis" xlink:to="loc_srtConsolidationItemsDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srtConsolidationItemsDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_srtConsolidationItemsAxis" xlink:to="loc_srtConsolidationItemsDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingSegmentsMember" xlink:label="loc_us-gaapOperatingSegmentsMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srtConsolidationItemsDomain" xlink:to="loc_us-gaapOperatingSegmentsMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaapStatementBusinessSegmentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapScheduleOfSegmentReportingInformationBySegmentTable" xlink:to="loc_us-gaapStatementBusinessSegmentsAxis" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaapSegmentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapStatementBusinessSegmentsAxis" xlink:to="loc_us-gaapSegmentDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaapSegmentDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapStatementBusinessSegmentsAxis" xlink:to="loc_us-gaapSegmentDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_TelecomAndPaymentServicesMember" xlink:label="loc_idtTelecomAndPaymentServicesMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapSegmentDomain" xlink:to="loc_idtTelecomAndPaymentServicesMember_0" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_Net2phoneMember" xlink:label="loc_idtNet2phoneMember_40"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapSegmentDomain" xlink:to="loc_idtNet2phoneMember_40" xlink:type="arc" order="42"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CorporateMember" xlink:label="loc_us-gaapCorporateMember_80"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapSegmentDomain" xlink:to="loc_us-gaapCorporateMember_80" xlink:type="arc" order="82"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaapRevenues_170"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapSegmentReportingInformationLineItems" xlink:to="loc_us-gaapRevenues_170" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="loc_us-gaapOperatingIncomeLoss_170"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapSegmentReportingInformationLineItems" xlink:to="loc_us-gaapOperatingIncomeLoss_170" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherOperatingIncomeExpenseNet" xlink:label="loc_us-gaapOtherOperatingIncomeExpenseNet_170"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapSegmentReportingInformationLineItems" xlink:to="loc_us-gaapOtherOperatingIncomeExpenseNet_170" xlink:type="arc" order="2"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/BusinessSegmentInformationDetailsTextual" xlink:title="00000073 - Disclosure - Business Segment Information (Details Textual)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/CommitmentsAndContingenciesDetails" xlink:title="00000074 - Disclosure - Commitments and Contingencies (Details)">
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LossContingenciesLineItems" xlink:label="loc_us-gaapLossContingenciesLineItems"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LossContingenciesTable" xlink:label="loc_us-gaapLossContingenciesTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_us-gaapLossContingenciesLineItems" xlink:to="loc_us-gaapLossContingenciesTable" xlink:type="arc" order="10" xbrldt:closed="true"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_deiLegalEntityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapLossContingenciesTable" xlink:to="loc_deiLegalEntityAxis" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:label="loc_deiEntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_deiLegalEntityAxis" xlink:to="loc_deiEntityDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:label="loc_deiEntityDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_deiLegalEntityAxis" xlink:to="loc_deiEntityDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_TelecomOperatorMember" xlink:label="loc_idtTelecomOperatorMember_0"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_deiEntityDomain" xlink:to="loc_idtTelecomOperatorMember_0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaapSubsequentEventTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaapLossContingenciesTable" xlink:to="loc_us-gaapSubsequentEventTypeAxis" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaapSubsequentEventTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaapSubsequentEventTypeAxis" xlink:to="loc_us-gaapSubsequentEventTypeDomain" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaapSubsequentEventTypeDomain_10"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_us-gaapSubsequentEventTypeAxis" xlink:to="loc_us-gaapSubsequentEventTypeDomain_10" xlink:type="arc" order="30"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaapSubsequentEventMember_30"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapSubsequentEventTypeDomain" xlink:to="loc_us-gaapSubsequentEventMember_30" xlink:type="arc" order="32"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_CommitmentsAndContingenciesTextualAbstract" xlink:label="loc_idtCommitmentsAndContingenciesTextualAbstract_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaapLossContingenciesLineItems" xlink:to="loc_idtCommitmentsAndContingenciesTextualAbstract_50" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccruedLiabilitiesCurrentAndNoncurrent" xlink:label="loc_us-gaapAccruedLiabilitiesCurrentAndNoncurrent_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtCommitmentsAndContingenciesTextualAbstract_50" xlink:to="loc_us-gaapAccruedLiabilitiesCurrentAndNoncurrent_50" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PurchaseObligation" xlink:label="loc_us-gaapPurchaseObligation_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtCommitmentsAndContingenciesTextualAbstract_50" xlink:to="loc_us-gaapPurchaseObligation_50" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherCommitment" xlink:label="loc_us-gaapOtherCommitment_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtCommitmentsAndContingenciesTextualAbstract_50" xlink:to="loc_us-gaapOtherCommitment_50" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_PerformanceBondsOutstanding" xlink:label="loc_idtPerformanceBondsOutstanding_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtCommitmentsAndContingenciesTextualAbstract_50" xlink:to="loc_idtPerformanceBondsOutstanding_50" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EscrowDeposit" xlink:label="loc_us-gaapEscrowDeposit_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtCommitmentsAndContingenciesTextualAbstract_50" xlink:to="loc_us-gaapEscrowDeposit_50" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:href="idt-20200430.xsd#idt_CashAndCashEquivalentsSubstantiallyRestricted" xlink:label="loc_idtCashAndCashEquivalentsSubstantiallyRestricted_50"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_idtCommitmentsAndContingenciesTextualAbstract_50" xlink:to="loc_idtCashAndCashEquivalentsSubstantiallyRestricted_50" xlink:type="arc" order="6"/>
</link:definitionLink>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/OtherExpenseIncomeNetDetails" xlink:title="00000075 - Disclosure - Other (Expense) Income, Net (Details)"/>
<link:definitionLink xlink:type="extended" xlink:role="http://idt.net/role/DefinedContributionPlanDetails" xlink:title="00000076 - Disclosure - Defined Contribution Plan (Details)"/>
</link:linkbase>

Top
Filing Submission 0001213900-20-014476   –   Alternative Formats (Word / Rich Text, HTML, Plain Text, et al.)

Copyright © 2024 Fran Finnegan & Company LLC – All Rights Reserved.
AboutPrivacyRedactionsHelp — Thu., Apr. 25, 8:20:57.1am ET