Lemma (morphology)

In morphology and lexicography, a lemma (plural lemmas or lemmata) is the canonical form, dictionary form, or citation form of a set of words (headword). In English, for example, run, runs, ran and running are forms of the same lexeme, with run as the lemma. Lexeme, in this context, refers to the set of all the forms that have the same meaning, and lemma refers to the particular form that is chosen by convention to represent the lexeme. In lexicography, this unit is usually also the citation form or headword by which it is indexed. Lemmas have special significance in highly inflected languages such as Arabic, Turkish and Russian. The process of determining the lemma for a given word is called lemmatisation. The lemma can be viewed as the chief of the principal parts, although lemmatisation is at least partly arbitrary.

In English, the citation form of a noun is the singular: e.g., mouse rather than mice. For multi-word lexemes that contain possessive adjectives or reflexive pronouns, the citation form uses a form of the indefinite pronoun one: e.g., do one's best, perjure oneself. In languages with grammatical gender, the citation form of regular adjectives and nouns is usually the masculine singular. If the language additionally has cases, the citation form is often the masculine singular nominative.

In many languages, the citation form of a verb is the infinitive: French , German , Spanish . In English it usually is the uninflected form of the verb (that is, "run", not "runs" or "running"); the present tense is used for some defective verbs (shall, can, and must have only the one form). In Latin, Ancient Greek, and Modern Greek (which has no infinitive), however, the first person singular present tense is normally used, though, occasionally, it may also be seen as the infinitive. (For contracted verbs in Ancient Greek, an uncontracted first person singular present tense is used to reveal the contract vowel, e.g. φιλέω philéō for φιλῶ philō "I love" [implying affection]; ἀγαπάω agapáō for ἀγαπῶ agapō "I love" [implying regard]). In Japanese, the non-past (present and future) tense is used.

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