Pi Approximation Day occurs every July 22nd. It celebrates pi, a key mathematical constant. Pi relates a circle's circumference to its diameter. William Jones introduced the π symbol in 1706 ...

National Pi Day is recognized today in the U.S. and around the world. Here's what to know about the quirky holiday, and how to celebrate.

Pi Day is the annual celebration of the mathematical constant, Pi. Here's what to know about its date, and why we celebrate it by eating pie.