Lemma (mathematics)

A lemma is a minor theorem used in the proof of a larger theorem.^[1] In most cases a lemma derives its importance from the theorem it is used to prove, but it can sometimes turn out to be more significant than originally thought, such as in the case of Euclid’s division lemma.^[2] There are no precise rules to distinguish between a lemma and a theorem. Different mathematicians may use either term in describing a true mathematical statement, depending on their perception of the importance of the result.^[3]

The term lemma is derived from the Greek λῆμμα, meaning something taken for granted.^[4]