Π

Symbol

 * 1)  Product over a set of like terms:
 * $$\prod_{n=1}^4 n^2 = 1^2 \cdot 2^2 \cdot 3^2 \cdot 4^2 = 576$$
 * 1)  A class (in some hierarchy of formulae, like the arithmetical hierarchy or polynomial hierarchy) of those formulae whose outermost quantifiers are universal quantifiers.

Usage notes

 * Though there exists a distinct code point for the purpose of the mathematical product, the upper case pi here continues to be used for convenience.

Etymology
From.

Letter

 * 1) The letter pi, the 16th letter of the ancient Greek alphabet.

Letter

 * 1) The uppercase letter pi (πι), the 16th letter of the modern Greek alphabet.