In mathematics, informal logic and argument mapping, a lemma (plural lemmas or lemmata) is a generally minor, proven proposition which is used as a stepping stone to a larger result. For that reason, it is also known as a "helping theorem" or an "auxiliary theorem". In many cases, a lemma derives its importance from the theorem it aims to prove, however, a lemma can also turn out to be more important than originally thought. The word "lemma" derives from the Ancient Greek λῆμμα ("anything which is received", such as a gift, profit, or a bribe).
Comparison with theorem
There is no formal distinction between a lemma and a theorem, only one of intention (see Theorem terminology). However, a lemma can be considered a minor result whose sole purpose is to help prove a more substantial theorem – a step in the direction of proof.
A good stepping stone can lead to many others. Some powerful results in mathematics are known as lemmas, first named for their originally minor purpose.[a] These include, among others:
While these results originally seemed too simple or too technical to warrant independent interest, they have eventually turned out to be central to the theories in which they occur.
|Look up lemma in Wiktionary, the free dictionary.|
- Fundamental lemma
- Inference objection
- List of lemmas
- Theorem terminology
- Conscientious mathematicians occasionally are given to the impulse of elevating the names to "theorem" rather than "lemma", but due to long use, the familiar, more humble name "lemma" invariably prevails.
- Higham, Nicholas J. (1998). Handbook of Writing for the Mathematical Sciences. Society for Industrial and Applied Mathematics. pp. 16. ISBN 0-89871-420-6.
- "Definition of lemma | Dictionary.com". www.dictionary.com. Retrieved 2019-11-28.
- Richeson, Dave (2008-09-23). "What is the difference between a theorem, a lemma, and a corollary?". David Richeson: Division by Zero. Retrieved 2019-11-28.