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 ...

Editor's note: A version of this story was published in March 2011. Get ready to roll out some dough, because it's Pi Day. What's that, you ask? Think back to geometry class. Pi represents the ratio ...

The number represented by pi (π) is used in calculations whenever something round (or nearly so) is involved, such as for circles, spheres, cylinders, cones and ellipses. Its value is necessary to ...

Tuesday is Pi Day, the annual celebration every March 14 for all things both Pi (the number) and pie (the food.) Pi, often shortened to 3.14, represents the ratio of a circle's circumference to its ...