Today is Pi Day, an annual celebration of the famous mathematical concept that has fascinated people for millenia. But what exactly is π (pronounced like the word "pie"), and where did the concept ...

It’s the most wonderful time of the year—for mathematicians, anyway. Pi Day is Friday, March 14. The relatively new holiday is a celebration of the mathematical calculation pi, or the infinite number ...

Pi, a mathematical constant denoted by the Greek letter π, is the ratio of a circle's circumference C to its diameter d: π = C/d. The circumference of a circle is, in turn, equal to 2πr, where r is ...