- (mathematics) The lemniscate constant, a transcendental constant representing the ratio of the perimeter of Bernoulli's lemniscate to its diameter; approximately 2.62205755.
- (mathematics) diameter of a model κ-plane:
- (astronomy) perihelion, etc.:
- (fluid dynamics) angular frequency of a wave
ϖ • (transliteration needed) (uppercase Π, lowercase π)
- Rare variant of the lower case letter pi (πι), the 16th letter of the modern Greek alphabet.