GRAMMATICALITY. In LINGUISTICS, conformity to the rules of a language as formulated by a GRAMMAR based on a theory of language description. The concept became prominent with the rise of GENERATIVE GRAMMAR in the 1960s, whose primary aim has been the construction of rules that would distinguish between the grammatical or well-formed SENTENCES and the ungrammatical, DEVIANT, or ill-formed sentences of a language.

Grammaticality has been differentiated from ACCEPTABILITY, which is based on the judgements by native speakers as to whether they would use a sentence or would consider it correct if they met it. Judgements about what is acceptable may reflect views that a sentence is nonsensical, implausible, illogical, stylistically inappropriate, or socially objectionable. Many linguists believe that they can filter out such considerations in their investigations of the facts of language. Many also believe that they can rely on their own introspection to provide samples of clearly grammatical and clearly ungrammatical sentences that would be adequate for compiling and testing the rules. Others consider that the examination of large quantities of data stored and organized by means of computers can yield additional and more reliable information on what constructions are possible and which are central or peripheral to the language. See CORPUS.

A sensitive issue regarding grammaticality is variability within a language, for example the extent to which sentences are grammatical for one regional or social variety but not another, or indeed for one idiolect rather than another. Non-standard varieties of a language have their own grammars, which will resemble to a greater or less extent the grammar of the standard varieties, so that a sentence may be grammatical in one non-standard variety but ungrammatical in a standard variety, and vice versa. Some sociolinguists believe that linguists should have as their objective the compilation of multilectal grammar: a grammar that would take into account all variation within a given language.