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.

Yet even after mathematicians worked out how to calculate pi accurately to over 100 decimal places at the start of the 18th century, we didn’t have an agreed symbol for the number.

National Pi Day is recognized on March 14 in the U.S. and around the world. Here's what to know about the quirky holiday, and how to celebrate.

Pi, which is the ratio of a circle's circumference to its diameter, is celebrated with its own holiday on March 14.

Going back to the holiday's roots, the mathematical symbol Pi is the ratio of the circumference of a circle to its diameter. The value of Pi is approximately 3.14, but it has infinite decimal ...