Celebrated annually on March 14, Pi ("π”) Day is a universal favorite with students and teachers. Though the American holiday, which honors the numerical constant representing the ratio of a circle's circumference to its diameter, typically begins with a classroom discussion of the symbol, it usually ends with a slice or two of delicious pie. The event is commemorated every March 14 because the irrational number, which continues infinitely without repetition or pattern, is widely recognized as 3.14.