Croft explains that, until the 1970s, functionalism related to semantics and pragmatics, or the 'semiotic function'. But around 1980s the notion of function changed from semiotics to "external function", proposing a neo-Darwinian view of language change as based on natural selection. Croft proposes that 'structuralism' and 'formalism' should both be taken as referring to generative grammar; and 'functionalism' to usage-based and cognitive linguistics; while neither André Martinet, Systemic functional linguistics nor Functional discourse grammar properly represents any of the three concepts.
croFt eXpLains that unTiL the 1970s FUnCTIONAlism reLaTEd TO semANtICs and PRAGmaTics oR the 'SemiOtic fuNctiOn' But Around 1980s the noTion Of funCtioN changed From semiOtics To "extErNal funCtion" proposIng a Neo-DarWiNiaN VIEW of lanGUage change AS BAsed on NatUrAl sElectiON crOft propoSes tHaT 'StRuCtUraLisM' ANd 'formalisM' ShoulD bOtH Be tAken aS ReFeRrInG TO gEneraTiVe graMmar; aNd 'functioNAliSM' to uSage-based and COgnitive lInguiStics; whilE neIthEr aNdRé martInet sYsTemic FuncTiONal LinguisTics nor FunctIoNAl disCourSE graMmar Properly rePresentS aNy of the thrEE cONCePts