Which number is so special that it’s celebrated in many countries around the world? It’s 3.14 … , pi, of course! Pi Day is celebrated each year on March 14.
 
That’s right, pi—the ratio of a circle’s circumference to its diameter, or (π = c/d)—has its own special celebration. 

Typically expressed as 3.14159 … or 3.14, pi’s digits go on indefinitely, and computers have calculated its decimals into the billions. Represented by the Greek letter, “π,” pi is a critical concept in pure mathematics and in the formulas of physics and engineering. Wherever there are circles, spheres, spirals, curves, rings, or waves, there is pi. It is also part of Heisenberg’s Uncertainty Principle, which defines how precisely we can know the state of the universe. 

Pi Day is observed annually on March 14 in countries that follow the month/day (mm/dd) date format, because the date, 3/14, corresponds to pi’s first three numerals. Pi Day celebrations include “pi-themed,” circle-shaped food such as pizza pies, fruit pies, cookies, or cupcakes, as well as educational events and activities to encourage appreciation of math.

Let's all encourage kids to celebrate math for math’s sake on Pi Day this year! It’s a great way to  help them learn to love math.