grammatic

listen to the pronunciation of grammatic
Английский Язык - Английский Язык
of or pertaining to grammar; "the grammatic structure of a sentence"; "grammatical rules"; "grammatical gender"
Grammatical

Grammatically, it's correct, but native speakers wouldn't say something like that. - It's grammatically correct, but native speakers wouldn't say that.

This sentence is grammatically correct. - This is a grammatically correct sentence.