Pi (letter)

Pi (uppercase/lowercase Π π), is the letter of the Greek alphabet, used to represent the "p" sound in Ancient and Modern Greek. In the system of Greek numerals, it has a value of 80. Letters that came from it include the Roman P and Cyrillic П.
In mathematics, the uppercase pi is used for the Pi product operator (for example. formula_1), similar to the way summation is used. The lowercase pi is used as the mathematical constant pi, also known as Archimedes's constant.