In the context of formal argumentation, proposition deduced from one or more axioms, the demonstration of which paves the way for the demonstration of a theorem that will follow.
Etymological Note
The word lemma comes from the Greek word lêmma (λημμα)that means “result” or “received” or even, by extension, “consequence”. In a mathematical context, the lemma is added to the statement of one or more axioms and thereby completes the argumentation, making it possible to demonstrate a new proposition (theorem).