Grammatical \Gram*mat"ic*al\, a. [L. grammaticus, grammaticalis; Gr. ? skilled in grammar, knowing one's letters, from ? a letter: cf. F. grammatical. See Grammar.]

1. Of or pertaining to grammar; of the nature of grammar; as, a grammatical rule.

2. According to the rules of grammar; grammatically correct; as, the sentence is not grammatical; the construction is not grammatical. --Gram*mat"ic*al*ly, adv. -- Gram*mat"ic*al*ness, n.

Source: Webster's Revised Unabridged Dictionary (1913)