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GMS Inc. – ‘10-Q’ for 7/31/20 – ‘EX-101.DEF’

On:  Thursday, 9/3/20, at 4:51pm ET   ·   For:  7/31/20   ·   Accession #:  1558370-20-10991   ·   File #:  1-37784

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

 9/03/20  GMS Inc.                          10-Q        7/31/20   83:8.2M                                   Toppan Merrill Bridge/FA

Quarterly Report   —   Form 10-Q
Filing Table of Contents

Document/Exhibit                   Description                      Pages   Size 

 1: 10-Q        Quarterly Report                                    HTML    987K 
 2: EX-31.1     Certification -- §302 - SOA'02                      HTML     33K 
 3: EX-31.2     Certification -- §302 - SOA'02                      HTML     34K 
 4: EX-32.1     Certification -- §906 - SOA'02                      HTML     26K 
 5: EX-32.2     Certification -- §906 - SOA'02                      HTML     26K 
12: R1          Document and Entity Information                     HTML     76K 
13: R2          Condensed Consolidated Balance Sheets               HTML    105K 
14: R3          Condensed Consolidated Balance Sheets               HTML     45K 
                (Parenthetical)                                                  
15: R4          Condensed Consolidated Statements of Operations     HTML     85K 
                and Comprehensive Income                                         
16: R5          Condensed Consolidated Statements of Stockholders'  HTML     73K 
                Equity (Unaudited)                                               
17: R6          Condensed Consolidated Statements of Cash Flows     HTML    115K 
18: R7          Business, Basis of Presentation and Summary of      HTML     50K 
                Significant Accounting Policies                                  
19: R8          Revenue                                             HTML     30K 
20: R9          Accounts Receivable                                 HTML     48K 
21: R10         Goodwill and Intangible Assets                      HTML    115K 
22: R11         Long-Term Debt                                      HTML    103K 
23: R12         Leases                                              HTML    118K 
24: R13         Income Taxes                                        HTML     26K 
25: R14         Stockholders' Equity                                HTML     49K 
26: R15         Equity-Based Compensation                           HTML     90K 
27: R16         Stock Appreciation Rights, Deferred Compensation    HTML     61K 
                and Redeemable Noncontrolling Interests                          
28: R17         Fair Value Measurements                             HTML     44K 
29: R18         Transactions With Related Parties                   HTML     26K 
30: R19         Commitments and Contingencies                       HTML     25K 
31: R20         Segments                                            HTML    146K 
32: R21         Earnings Per Common Share                           HTML     49K 
33: R22         Business, Basis of Presentation and Summary of      HTML     70K 
                Significant Accounting Policies (Policies)                       
34: R23         Accounts Receivable (Tables)                        HTML     48K 
35: R24         Goodwill and Intangible Assets (Tables)             HTML    115K 
36: R25         Long-Term Debt (Tables)                             HTML    102K 
37: R26         Leases (Tables)                                     HTML    139K 
38: R27         Stockholders' Equity (Tables)                       HTML     45K 
39: R28         Equity-Based Compensation - (Tables)                HTML     89K 
40: R29         Stock Appreciation Rights, Deferred Compensation    HTML     57K 
                and Redeemable Noncontrolling Interests (Tables)                 
41: R30         Fair Value Measurements (Tables)                    HTML     38K 
42: R31         Segments (Tables)                                   HTML    150K 
43: R32         Earnings Per Common Share (Tables)                  HTML     48K 
44: R33         Business, Basis of Presentation and Summary of      HTML     24K 
                Significant Accounting Policies - Business                       
                (Details)                                                        
45: R34         Business, Basis of Presentation and Summary of      HTML     54K 
                Significant Accounting Policies - Insurance                      
                Liabilities (Details)                                            
46: R35         Revenue (Details)                                   HTML     30K 
47: R36         Accounts Receivable - Trade Accounts And Notes      HTML     34K 
                Receivable (Details)                                             
48: R37         Accounts Receivable - Change In Allowance           HTML     33K 
                (Details)                                                        
49: R38         Goodwill and Intangible Assets - Goodwill           HTML     34K 
                (Details)                                                        
50: R39         Goodwill and Intangible Assets - Definite-Lived     HTML     66K 
                Intangible Assets (Details)                                      
51: R40         Goodwill and Intangible Assets - Amortization       HTML     28K 
                (Details)                                                        
52: R41         Goodwill and Intangible Assets - Estimated          HTML     36K 
                Aggregate Amortization Expense (Details)                         
53: R42         Goodwill and Intangible Assets - Indefinite-Lived   HTML     25K 
                Intangible Assets (Details)                                      
54: R43         Long-Term Debt - Components (Details)               HTML     46K 
55: R44         Long-Term Debt - Acquisition Debt (Details)         HTML     42K 
56: R45         Long-Term Debt - Asset-Based Lending Facility       HTML     39K 
                (Details)                                                        
57: R46         Long-Term Debt - Canadian Revolving Credit          HTML     35K 
                Facility (Details)                                               
58: R47         Long-Term Debt - Maturities (Details)               HTML     65K 
59: R48         Leases (Details)                                    HTML     47K 
60: R49         Leases - Supplemental cash flow information         HTML     35K 
                (Details)                                                        
61: R50         Leases - Other information (Details)                HTML     43K 
62: R51         Leases - Future minimum lease payments under        HTML     61K 
                non-cancellable leases (Details)                                 
63: R52         Income Taxes (Details)                              HTML     32K 
64: R53         Stockholders' Equity - Exchangeable Shares, Share   HTML     38K 
                Repurchase Program and Secondary Public Offering                 
                (Details)                                                        
65: R54         Stockholders' Equity - Accumulated Other            HTML     39K 
                Comprehensive Loss (Details)                                     
66: R55         Equity-Based Compensation - Stock Option Activity   HTML     86K 
                (Details)                                                        
67: R56         Equity-Based Compensation - Black Scholes Options   HTML     37K 
                - Pricing Model (Details)                                        
68: R57         Equity-Based Compensation - Restricted Stock Units  HTML     47K 
                (Details)                                                        
69: R58         Equity-Based Compensation - Employee Stock          HTML     37K 
                Purchase Plan (Details)                                          
70: R59         Stock Appreciation Rights, Deferred Compensation    HTML     47K 
                and Redeemable Noncontrolling Interests (Details)                
71: R60         Fair Value Measurements (Details)                   HTML     49K 
72: R61         Transactions With Related Parties - Purchased       HTML     32K 
                Inventories (Details)                                            
73: R62         Segments (Details)                                  HTML     30K 
74: R63         Segments - Net Sales, Adjusted EBITDA and Certain   HTML     44K 
                Other Measures (Details)                                         
75: R64         Segments - Reconciliation of Net Income to          HTML     56K 
                Adjusted EBITDA (Details)                                        
76: R65         Segments - Net Sales by Main Product Lines          HTML     34K 
                (Details)                                                        
77: R66         Segments - Net sales by major geographic area       HTML     32K 
                (Details)                                                        
78: R67         Segments - Property and equipment, net, by major    HTML     30K 
                geographic area (Details)                                        
79: R68         Earnings Per Common Share (Details)                 HTML     51K 
81: XML         IDEA XML File -- Filing Summary                      XML    150K 
11: XML         XBRL Instance -- gms-20200731x10q_htm                XML   2.13M 
80: EXCEL       IDEA Workbook of Financial Reports                  XLSX     92K 
 7: EX-101.CAL  XBRL Calculations -- gms-20200731_cal                XML    198K 
 8: EX-101.DEF  XBRL Definitions -- gms-20200731_def                 XML    484K 
 9: EX-101.LAB  XBRL Labels -- gms-20200731_lab                      XML   1.36M 
10: EX-101.PRE  XBRL Presentations -- gms-20200731_pre               XML    954K 
 6: EX-101.SCH  XBRL Schema -- gms-20200731                          XSD    157K 
82: JSON        XBRL Instance as JSON Data -- MetaLinks              356±   543K 
83: ZIP         XBRL Zipped Folder -- 0001558370-20-010991-xbrl      Zip    226K 


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


This Exhibit is an XBRL XML File.


                                                                                                                                                                                
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<roleRef xlink:type="simple" xlink:href="gms-20200731.xsd#DisclosureLongTermDebtMaturitiesDetails" roleURI="http://www.gms.com/role/DisclosureLongTermDebtMaturitiesDetails" xmlns="http://www.xbrl.org/2003/linkbase"/>
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<roleRef xlink:type="simple" xlink:href="gms-20200731.xsd#DisclosureLeasesOtherInformationDetails" roleURI="http://www.gms.com/role/DisclosureLeasesOtherInformationDetails" xmlns="http://www.xbrl.org/2003/linkbase"/>
<roleRef xlink:type="simple" xlink:href="gms-20200731.xsd#DisclosureIncomeTaxesDetails" roleURI="http://www.gms.com/role/DisclosureIncomeTaxesDetails" xmlns="http://www.xbrl.org/2003/linkbase"/>
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<roleRef xlink:type="simple" xlink:href="gms-20200731.xsd#DisclosureStockholdersEquityAccumulatedOtherComprehensiveLossDetails" roleURI="http://www.gms.com/role/DisclosureStockholdersEquityAccumulatedOtherComprehensiveLossDetails" xmlns="http://www.xbrl.org/2003/linkbase"/>
<roleRef xlink:type="simple" xlink:href="gms-20200731.xsd#DisclosureEquityBasedCompensationStockOptionActivityDetails" roleURI="http://www.gms.com/role/DisclosureEquityBasedCompensationStockOptionActivityDetails" xmlns="http://www.xbrl.org/2003/linkbase"/>
<roleRef xlink:type="simple" xlink:href="gms-20200731.xsd#DisclosureEquityBasedCompensationBlackScholesOptionsPricingModelDetails" roleURI="http://www.gms.com/role/DisclosureEquityBasedCompensationBlackScholesOptionsPricingModelDetails" xmlns="http://www.xbrl.org/2003/linkbase"/>
<roleRef xlink:type="simple" xlink:href="gms-20200731.xsd#DisclosureEquityBasedCompensationRestrictedStockUnitsDetails" roleURI="http://www.gms.com/role/DisclosureEquityBasedCompensationRestrictedStockUnitsDetails" xmlns="http://www.xbrl.org/2003/linkbase"/>
<roleRef xlink:type="simple" xlink:href="gms-20200731.xsd#DisclosureEquityBasedCompensationEmployeeStockPurchasePlanDetails" roleURI="http://www.gms.com/role/DisclosureEquityBasedCompensationEmployeeStockPurchasePlanDetails" xmlns="http://www.xbrl.org/2003/linkbase"/>
<roleRef xlink:type="simple" xlink:href="gms-20200731.xsd#DisclosureStockAppreciationRightsDeferredCompensationAndRedeemableNoncontrollingInterestsDetails" roleURI="http://www.gms.com/role/DisclosureStockAppreciationRightsDeferredCompensationAndRedeemableNoncontrollingInterestsDetails" xmlns="http://www.xbrl.org/2003/linkbase"/>
<roleRef xlink:type="simple" xlink:href="gms-20200731.xsd#DisclosureFairValueMeasurementsDetails" roleURI="http://www.gms.com/role/DisclosureFairValueMeasurementsDetails" xmlns="http://www.xbrl.org/2003/linkbase"/>
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<roleRef xlink:type="simple" xlink:href="gms-20200731.xsd#DisclosureSegmentsNetSalesAdjustedEbitdaAndCertainOtherMeasuresDetails" roleURI="http://www.gms.com/role/DisclosureSegmentsNetSalesAdjustedEbitdaAndCertainOtherMeasuresDetails" xmlns="http://www.xbrl.org/2003/linkbase"/>
<roleRef xlink:type="simple" xlink:href="gms-20200731.xsd#DisclosureSegmentsNetSalesByMainProductLinesDetails" roleURI="http://www.gms.com/role/DisclosureSegmentsNetSalesByMainProductLinesDetails" xmlns="http://www.xbrl.org/2003/linkbase"/>
<roleRef xlink:type="simple" xlink:href="gms-20200731.xsd#DisclosureSegmentsNetSalesByMajorGeographicAreaDetails" roleURI="http://www.gms.com/role/DisclosureSegmentsNetSalesByMajorGeographicAreaDetails" xmlns="http://www.xbrl.org/2003/linkbase"/>
<roleRef xlink:type="simple" xlink:href="gms-20200731.xsd#DisclosureSegmentsPropertyAndEquipmentNetByMajorGeographicAreaDetails" roleURI="http://www.gms.com/role/DisclosureSegmentsPropertyAndEquipmentNetByMajorGeographicAreaDetails" xmlns="http://www.xbrl.org/2003/linkbase"/>
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<link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
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<link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
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<loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2017/country-2017-01-31.xsd#country_US" xlink:label="country_US"/>
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1 Subsequent Filing that References this Filing

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

11/10/20  GMS Inc.                          S-8        11/10/20    3:87K                                    Toppan Merrill/FA


1 Previous Filing that this Filing References

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

 5/16/16  GMS Inc.                          S-1/A                 11:5.6M                                   Toppan Merrill-FA
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