Pi

The symbol for Pi is p, or simply pi, and has an approximate value of 3.14159265. Also, pi is an irrational number.
Pi occurs in various mathematical calculations, such as the circumference or the area of a circle. Pi is also applied to mathematical problems involving the lengths of arcs or other curves, the areas of ellipses, sectors, and other curved surfaces, and the volumes of solids. It is also used in various formulas of physics and engineering.
Computers in the late 20th century carried pi to more than 100,000,000 decimal places. [RA] {EB}