Pi

pi (symbol <math>\pi</math>) is the mathematical symbol used to represent the number that is the ratio of the circumference of any circle to its diameter.

Pi is fundamentally important in mathematics.

It can be shown that pi is a trancendental number. It is also an irrational number. Its decimal expansion is therefore infinite and non-repeating. The first few decimal digits are:

<math>3.141592653589792...</math>

Pi is also the basis for the radian angular measure.