Pi

[Sarah]

The transcendental number which refers to the definition (in which it is multiplied by the radius of a circle) of the area of the circle. (or if multiplied by the diameter, defines the circumfrence).

[Rihanna]

Pi is an [irrational number] (meaning the digits [never end] or have a repeating pattern) that is the ratio of the circumference of a circle to its diameter...this ratio is a constant for any circle, regardless [of size].