gram·mar 
(grămər)
(grămər)n.
1.
a. The study of how words and their component parts combine to form sentences.
b. The study of structural relationships in language or in a language, sometimes including pronunciation, meaning, and linguistic history.
2.
a. The system of inflections, syntax, and word formation of a language.
b. The system of rules implicit in a language, viewed as a mechanism for generating all sentences possible in that language.
3.
a. A normative or prescriptive set of rules setting forth the current standard of usage for pedagogical or reference purposes.
b. Writing or speech judged with regard to such a set of rules.
4. A book containing the morphologic, syntactic, and semantic rules for a specific language.
5.
a. The basic principles of an area of knowledge: the grammar of music.
b. A book dealing with such principles.
[Middle English gramere, from Old French gramaire, alteration of Latin grammatica, from Greek grammatikē, from feminine of grammatikos, of letters, from gramma, grammat-, letter; see gerbh- in the Appendix of Indo-European roots.]