Lemma

From The ICAL TEFL wiki

Simply put, a lemma is the headword of a set of forms related to it. For example, do, does, did and doing are forms of the same lexeme, with do as the lemma.

In morphology a lemma is the standard form of a lexeme. The lexeme refers to the set of all the forms that have the same meaning, and the lemma refers to the particular form that is chosen by convention to represent the lexeme.

In lexicography, a lemma is usually the headword by which it is indexed. In a dictionary, the lemma go represents the inflected forms go, goes, going, went, and gone. The relationship between an inflected form and its lemma is usually denoted by an angle bracket: "went" < "go".

In English, the headword of a noun is the nomintiave singular: e.g., mouse rather than mice. For multi-word lexemes which contain possessive adjectives or reflexive pronouns, the headword uses a form of the indefinite pronoun one: e.g. do one's best, perjure oneself. With verbs a lemma is usually either the infinitive or the present tense in the first person singular.

Lemmas are used often in corpora linguistics for determining word frequency.