Unnecessary background...

Pi is a mathematical constant which represents the ratio of any circle's circumference to its diameter, which is the same as the ratio of a circle's area to the square of its radius. It is approximately equal to 3.14159. Pi is one of the most important mathematical constants: many formulae from mathematics, science, and engineering involve use pi.

Pi is an irrational and transcendental number, which means that it cannot be expressed as a fraction and no finite sequence of algebraic operations on integers (powers, roots, sums, etc.) could ever produce it. Throughout the history of mathematics, much effort has been made to determine its exact value.

There you have it. My favorite is red raspberry.