noun
lexeme
Linguistics term for the abstract unit of vocabulary that encompasses all inflected forms of a word.
「走る」「走った」「走らない」は同じ語彙素に属する。
"走る", "走った", and "走らない" belong to the same lexeme.
Word: a general term for a word as a surface form, whereas 語彙素 is a technical linguistics concept.
Compound of 語彙 (vocabulary) and 素 (element), likely a modern calque from Western linguistics.