The Collaborative International Dictionary
Grammaticalness
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.]
Of or pertaining to grammar; of the nature of grammar; as, a grammatical rule.
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.
Wiktionary
grammaticalness
n. (context of language English) The state or attribute of obeying the rules of grammar; grammatical correctness.