Meaning of GRAMMAR in English

vi to discourse according to the rules of grammar; to use grammar.

2. grammar ·noun treatise on the elements or principles of any science; as, a grammar of geography.

3. grammar ·noun a treatise on the principles of language; a book containing the principles and rules for correctness in speaking or writing.

4. grammar ·noun the art of speaking or writing with correctness or according to established usage; speech considered with regard to the rules of a grammar.

5. grammar ·noun the science which treats of the principles of language; the study of forms of speech, and their relations to one another; the art concerned with the right use aud application of the rules of a language, in speaking or writing.

Webster English vocab.      Английский словарь Webster.