põhisõnast

Põhisõna is a linguistic term used in Estonian to denote the base form or lemma of a word, the form from which other inflected forms are derived. It acts as the reference point for analyses of word families and for dictionary entries. In practice, the põhisõna is the form that lexicographers choose as the headword and that computational systems map other forms back to.

In Estonian grammar the exact designation of the põhisõna depends on word class. For verbs, the põhisõna is typically the infinitive, for example lugema (to read), from which tense, mood and other verbal forms are produced. For nouns, the põhisõna is usually the nominative singular, which functions as the dictionary form and the anchor for inflection patterns. For adjectives, the base form corresponds to the positive degree in its basic form. Because Estonian employs extensive case and number inflection, many inflected forms share a single põhisõna as their underlying representation.

In lexicography and natural language processing, the põhisõna is commonly called the lemma. Lemmatization and dictionary lookups reduce word forms to the põhisõna to normalize data, analyze meaning, or establish word families. The concept also supports etymological study and the analysis of productive affixes. While the term is mainly used in linguistic and educational contexts, understanding the põhisõna helps clarify how Estonian words relate across different inflected forms.