fusional

Fusional is a term in linguistic morphology describing a type of word formation in which morphemes fuse multiple grammatical categories into a single form. In fusional systems, a single affix or stem change can encode tense, mood, voice, person, number, case, and gender at once. Morphological boundaries are often not easily segmented, and forms may show irregularities or internal vowel changes.

Fusional languages are contrasted with agglutinative languages, where each affix typically marks a single category, and with isolating languages, which rely more on word order and function words than on affixes. In fusional systems, a given affix may carry several grammatical meanings, and the same meaning can be expressed by several phonological forms due to stem changes.

Major examples of fusional traits occur in many Indo-European languages. Latin verbs use endings that encode person, number, tense, and mood, while Latin nouns encode case and number within their endings. Russian illustrates fusion in nouns and adjectives, marking case, number, and gender in inflected forms; Russian verbs encode tense, aspect, mood, person, and number, often with stem changes. German displays vowel alternations in strong verbs and endings that combine case and number with person and mood. Spanish and other Romance languages also show fusional patterns, especially in verb conjugations, though they can blend with analytic features.

In typology, fusional languages lie on a continuum with agglutinative and isolating languages. The degree of fusion varies across languages and even within a single language, producing a spectrum rather than a rigid categorization.