lexical unit
Definition - (Aka lexeme | lexical item)

A set of words that has the same base form.

For example, run, runs, ran and running are all members of the same lexical unit; the base form is run.

Oxford English Dictionary -
The term's first citation is from 1951:
"In the Oxford English Dictionary there are nearly half a million lexical units."
(G. A. Miller Lang. & Communication iv. 89)

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