 Chomsky (1986) introduced the neologism ‘I-language’ in part to disambiguate the word ‘grammar’. In earlier generative Essentialist literature, ‘grammar’ was (deliberately) ambiguous between (i) the linguist’s generative theory and (ii) what a speaker knows when they know a language. ‘I-language’ can be regarded as a replacement for Bever’s term ‘psychogrammar’ (see also George 1989): it denotes a mental or psychological entity (not a grammarian’s description of a language as externally manifested).