yksimuotoinen

Yksimuotoinen is a linguistic term used to describe a word that has a single morphological form and therefore does not change across grammatical categories such as case, number, person, tense, or mood. In Finnish language description, the term is used to distinguish invariable words from those that participate in inflectional paradigms. A yksimuotoinen word retains the same form in standard grammatical contexts.

In practice, a word is considered yksimuotoinen if its form remains constant across typical inflectional contexts. This designation is often applied to function words and other closed-class items that do not display productive inflection in the language. Common candidates include conjunctions, certain adverbs, interjections, and fixed particles. For example, conjunctions like ja (and) and tai (or) are typically invariable and thus treated as yksimuotoinen. Likewise, several adverbs such as aina (always) or hyvin (well) commonly do not take inflectional endings in everyday usage, and may be analyzed as yksimuotoinen in linguistic descriptions, although some contexts or dialects can introduce variations.

The concept helps both theoretical and practical analyses. For theoretical linguistics, it provides a contrast to monimuotoinen words, which form multiple paradigms. For computational morphology and lexicography, recognizing yksimuotoinen forms simplifies parsing and dictionary entry design, since such words require no inflectional paradigm. It is important to note that the classification can be language- and dialect-dependent; what is invariable in one variety may show limited variation in another.