- left turn
- left twisted helix
- left uniformity
- left unique relation
- left unit
- left-unitary kernel
- left unit element
- left unit subsemigroup
- left unity
- left universal solution
- left vector space
- left ventricle
- left ventricular ejection fraction
- leftward acceleration
- leftward extraction rule
- left weak dimension
- left-wing film movement
- left-wing movement in music
- left wing of an occurrence
- left zero
- left zero divisor
- left zero element
- left zeroid
- left zero morphism
- left zero semigroup