lemma

In linguistics, a lemma is the form of a word chosen from the set of all of the forms of the word to be the canonical, or default, representation of the lexeme, the meaning shared by all of the word’s forms.

For example, walk, walking, walked, walks, are different forms of the same lexeme; their basic meaning is the same. The word is chosen to be the canonical representation of the lexeme, the lemma, is walk.

Lemmas are also known as headwords.