lexeme

In linguistics, a lexeme is the abstract unit of lexical meaning that underlies a family of related word forms. The various inflected or derived forms that realize a single lexeme share core meaning, even though they appear differently in speech or writing. For example, the English verb eat has the lexeme eat, with surface forms such as eats, eating, and ate belonging to the same underlying unit.

A closely related concept is the lemma, often described as the canonical or dictionary form used to represent a lexeme. While many analyses treat the lemma as the same as the lexeme, others distinguish them or use the term differently across languages and frameworks. In practice, dictionaries and corpora typically organize entries by lexemes or lemmas, depending on the adopted convention.

Lexemes are the building blocks of a language's lexicon. They are abstract entities used in linguistic description and computational processing to group related word forms that share meaning and behavior in syntax. They are distinct from morphemes, which are the smallest units of meaning; a single lexeme may comprise multiple morphemes when inflected or derived.

The treatment of multiword expressions varies by framework. Some analyses treat certain idioms or fixed phrases as single lexemes because they function as unit meanings and syntactic wholes, while others analyze them as sequences of separate lexemes and words.

Overall, the concept of a lexeme helps linguists describe how word forms relate to underlying meanings, across morphologies and across languages, within the organized structure of a language’s lexicon.