<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-08-22</periodOfReport>
    <issuer>
        <issuerCik>0000097210</issuerCik>
        <issuerName>TERADYNE INC</issuerName>
        <issuerTradingSymbol>TER</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001239379</rptOwnerCik>
            <rptOwnerName>ROGAS EDWARD JR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>TERADYNE, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>321 HARRISON AVENUE</rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02118</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
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Buy)</value></securityTitle><conversionOrExercisePrice><value>9.5938</value></conversionOrExercisePrice><transactionDate><value>2003-08-22</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>26400</value></transactionShares><transactionPricePerShare><value>9.5938</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>1998-08-27</value><footnoteId id="F1"/></exerciseDate><expirationDate><value>2003-08-27</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common 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Buy)</value></securityTitle><conversionOrExercisePrice><value>9.5938</value></conversionOrExercisePrice><transactionDate><value>2003-08-25</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>18600</value></transactionShares><transactionPricePerShare><value>9.5938</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>1998-08-27</value><footnoteId id="F1"/></exerciseDate><expirationDate><value>2003-08-27</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Shares</value></underlyingSecurityTitle><underlyingSecurityShares><value>18600</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>536381</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeTransaction></derivativeTable><footnotes><footnote id="F1">This option is granted under Teradyne's 1991 Employee Stock Option Plan, as amended, and is exerciseable at a rate of 20% on 8/27/98 and 20% per year thereafter, commencing on 8/27/99.</footnote></footnotes><remarks/><ownerSignature><signatureName>Eileen Casal, General Counsel, by power of attorney</signatureName><signatureDate>2003-08-26</signatureDate></ownerSignature></ownershipDocument>

