A grammar can be regarded as a theory of a language; it is 'descriptively adequate' to the extent that it correctly describes the intrinsic competence of the idealized native speaker [...] 'a linguistic theory is descriptively adequate' if it makes a descriptively adequate grammar available for each natural language.
- Chomsky (1969), a pag.24

[…] a descriptively adequate grammar [...] - a grammar that [...] assigns structural descriptions to sentences in accordance with the linguistic competence of the native speaker.
- Chomsky (1969), a pag.34