Accidence

Accidence is the branch of grammar that concerns inflection—the changes that words undergo to express grammatical categories rather than meaning derived from word order or derivation. It covers how nouns, pronouns, adjectives, and verbs alter their form to signal case, number, and gender for nouns and adjectives; and person, number, tense, mood, and voice for verbs.

In traditional grammar, accidence describes the paradigms of words—the set of their inflected forms—often organized into declensions for nouns and adjectives and conjugations for verbs. By contrast, syntax studies how words combine and relate in sentences, while derivation concerns the formation of new words from existing roots.

The extent of accidence varies by language. Highly inflected languages such as Latin, Russian, and Greek have extensive noun declensions and verb conjugations, with many endings that express numerous grammatical categories. English has relatively limited inflection, with plural and possessive noun forms and verb tense and agreement mostly carried by auxiliary constructions and irregular forms. Some languages exhibit gendered agreement in adjectives or a rich case system for nouns and pronouns.

Etymology and usage: the term originates from Latin grammar and has been retained in traditional or pedagogical descriptions of inflection. In contemporary linguistics, inflection is the broader term, and accidence is more commonly encountered in historical or descriptive discussions of inflectional paradigms.