General terms:
* Syntax: Refers to the rules of sentence structure.
* Morphology: Deals with the structure of words and how they are formed.
* Linguistics: The broader study of language, encompassing grammar, phonetics, semantics, etc.
* Language rules: A general term for the principles governing how language is used.
More specific terms:
* Grammatical structure: Emphasizes the arrangement of words in sentences.
* Grammatical correctness: Focuses on the adherence to established rules.
* Language conventions: Refers to the accepted ways of using language.
* Language usage: Encompasses both grammar and style.
The best term to use will depend on the context and the specific aspect of grammar you are discussing.