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"Grammar is important because it is the language that makes it possible for us to talk about language . Grammar names the types of words and word groups that make up sentences not only in English but in any language. As human beings, we can put sentences together even as children—we can all do grammar.

Appropriateness noun – The quality or state of being especially suitable or fitting.

Correctness (https://thesaurus.plus/thesaurus/correctness) is a synonym for appropriateness (https://thesaurus.plus/thesaurus/appropriateness) in suitability (https://thesaurus.plus/thesaurus/suitability) topic. In some cases you can use "Correctness" instead a noun (https://thesaurus.plus/synonyms/appropriateness/category/noun) "Appropriateness".