Grammar (noun)

1. The whole system and structure of a language or of languages in general.
2. The study of the rules for forming words, phrases, clauses, and sentences in a language.

Origin:

Late middle english: from old french gramaire, via latin from greek grammatike (tekhnē) "(art) of letters", from gramma "letter".

Examples:

1. She was teaching grammar to her students.
2. He needed to brush up on his grammar before taking the test.
3. The book is a guide to English grammar.
4. The software checks grammar and spelling.
5. Grammar is an essential part of learning a new language.