HETEROCLITON, in Grammar, an irregular or anomalous word, which either in declension, conjugation, or regimen, deviates from the ordinary rules of grammar. The word is Greek, ἰσαγωγέαλυτος; formed of ἰσαγωγή, alter, "another, different;" and λυτος, "I decline."

Heteroclite is more peculiarly applied to nouns which vary or are irregular in point of declension; having fewer cases, numbers, &c. than ordinary; or that are of one declension in one number, and another in another: as Hoc vas, vasit; hec vasa, vasorum.