According to Math Open Reference, pi is a mathematical constant obtained by dividing the circumference of any circle by its diameter. Pi is about 22/7 or 3.142. However, no one knows its exact value.

Pi is known as an irrational number. When calculated, its decimal places are unending, and the numbers have no pattern of repetition. Therefore, it cannot be described as a ratio of two integers. The ancient Greek mathematician Archimedes is believed to be the first to calculate pi, which bears the same symbol as the 16th letter of the Greek alphabet. In 1882 German mathematician, Ferdinand von Lindemann, proved that pi was transcendental, meaning it's not the root of any equation that had rational numbers for coefficients. His work finally proved that it's impossible to square a circle.