arithmetic-geometric mean inequality
Generally, for a set of numbers 
with equality if and only if all 
take the same value. This inequality is often abbreviated to AM-GM.
- left and right derivative
- left inverse
- left‐handed system
- Legendre, Adrien‐Marie
- Legendre polynomials
- Legendre's conjecture
- Legendre's differential equation
- Legendre symbol
- Leibniz, Gottfried Wilhelm
- Leibniz's integral rule
- Leibniz's Theorem
- lemma
- length
- length
- length of an arc
- Leonardo da Vinci
- Leonardo of Pisa
- leptokurtic
- level set
- lever
- LHS
- L'Hôpital, Guillaume François Antoine, Marquis de
- L'Hôpital's rule
- liar paradox
- Lie algebra