Perusverbi

Perusverbi is a term used in Finnish-language grammar to denote the base or citation form of a verb. The word combines perus (basic) and verbi (verb). In practice it usually refers to the first infinitive, the uninflected dictionary form that ends in -a or -ä (for example puhua "to speak", syödä "to eat"). This form provides the verbal stem and is used as the starting point for forming other tenses, moods and participles.

In descriptive and pedagogical contexts, perusverbi functions as the canonical label for a verb entry and the reference for conjugation patterns. From the perusverbi one derive personal forms (present, past), the negative construction, conditional and potential moods, passive forms, and non-finite forms such as the other infinitives and participles. Finnish verbs are grouped into conjugation types based on how their stems change from the perusverbi when inflected.

While perusverbi typically denotes the first infinitive in Finnish, the precise notion of a "base" can vary in linguistic analysis, where researchers may distinguish between citation form, lexical stem and productive stems used in derivation. The term is most often encountered in grammar descriptions, language teaching materials and dictionaries.