: a part of grammar that deals with inflections (see inflectionsense 2a)
Inflectional morphology studies the way in which words vary (or "in-flect"), in order to express grammatical contrasts in sentences, such as singular/plural or past/present tense. In older grammar books, this branch of the subject was referred to as "accidence." David Crystal
Grammar has become that branch of linguistics that deals with a language's inflexions (accidence), other structures of words (morphology), its phonetics system (phonology), and the arrangement of its words in sentences (syntax). Philip Howard
Word History
Etymology
Middle English accidens "set of grammatical endings," borrowed from Late Latin accidentia "categories applicable to a word class (such as gender, number, and case for nouns)," from neuter plural of Latin accident-, accidens "contingent attribute" — more at accident