See also: Π [U+03A0 GREEK CAPITAL LETTER PI], ∏ [U+220F N-ARY PRODUCT], ㄇ [U+3107 BOPOMOFO LETTER M], ㅠ, and Appendix:Variations of "p"
- (mathematics) An irrational constant representing the ratio of the circumference of a circle to its diameter; approximately 3.14159265.
- (particle physics) pion, pi meson
- (mathematics) homotopy group
- (mathematics) prime-counting function