A <lexeme> is an abstract vocabulary item whose different grammatical forms are treated as instances of the same item. It separates lexical identity from the particular form occurring in an utterance. An inflectional description can therefore connect several forms without treating each as an unrelated entry.<Lexeme in the INLP Linguistic Glossary>[Definition, abstract grouping and inflectional categories]{ref}

For example, `walk`, `walks`, `walked` and `walking` can belong to the <lexeme> conventionally represented as `WALK`. Their differences involve <inflection>; forming a new item through <derivational morphology> is a different relation. A <lemma (linguistics)> is the conventional citation form used to label an entry, rather than the entire abstraction being represented.

This distinction matters when counting a <text corpus>. Counts of the exact form `walked` answer a different question from counts pooling all the specified forms of `WALK`. The grouping procedure must also handle ambiguous forms: spelling alone need not determine which <lexeme> a use instantiates.


 Lexeme (source code)