According to the Merriam Webster Dictionary:
The mathematical value of π, or pi, begins “3.14…” so March 14 (3/14) is considered to be International Pi Day.
Pi is the English spelling of the sixteenth letter of the Greek alphabet. It means “the symbol π denoting the ratio of the circumference of a circle to its diameter,” and also means “the ratio itself : a . . . → Read More: All about the Pi(e)