A fusional language (also called inflecting language) is a type of synthetic language, distinguished from agglutinative languages by its tendency to "squish together" many morphemes in a way which can be difficult to segment.

The canonical examples of fusional languages are Latin and German, with Dutch as a close follow-up. All Indo-European languages are fusional. Another notable group of fusional languages is the Semitic languages group.

A good illustration of fusionality in language is the Latin word boni, "good men". The ending -i denotes masculine gender, nominative case, and plural number. Changing any of these features requires replacement of the suffix -i with something else.

A feature that distinguishes fusional languages from agglutinating ones is the occurrence of irregular forms: this could not or hardly happen in agglutinating language since the synthetic elements retain a meaning of their own. Fusional languages are generally believed to have descended from agglutinating languages, though there is no linguistic evidence in the form of attested language changes to confirm this view. On the other hand, fusional languages generally tend to lose their inflection over the centuries—some languages much more quickly than others. For example, Slovenian, Lithuanian, and Armenian are about as fusional as Proto-Indo-European, but modern English and Afrikaans are nearly analytic.

Fusional languages | Synthetic languages

Yezh enteuzel | Flekterende sprog | Fusionaler Sprachbau | Lengua fusional | Langue fusionnelle | Flekterende språk | 屈折语