Perusmuotoa

Perusmuoto, or lemma, is the base form of a word used as the canonical entry form in Finnish grammar and dictionaries. It is the form from which other inflected forms are derived and is the form typically used for lemmatization in language processing. The perusmuoto helps identify a word’s basic meaning and part of speech despite the many possible endings or inflections in a sentence.

For nouns, the perusmuoto is usually the singular nominative form. For example, koira is the perusmuoto of the noun meaning dog; other forms include koiran (genitive), koiraa (partitive), and koirassa (in the dog). Verbs have their perusmuoto in the first infinitive; for example, kirjoittaa (to write) is the perusmuoto, and verbs are conjugated from this form to show tense and mood (jotun kirjoitan, kirjoitat, kirjoittavat, etc.). Adjectives use the positive base form as perusmuoto, such as iso meaning big; adjectives then inflect for degree and case (isompi, isoin, etc.).

Other word classes also have lemmas that function as perusmuotoja in dictionaries. In practice, the perusmuoto is central to linguistic analysis, lexicon design, and natural language processing, where algorithms reduce words to their base forms to compare meaning and syntax across inflected variants. While the perusmuoto is often clear, some words may have irregular or multiple lemmas in specific contexts, requiring reference to a reliable dictionary.