You’ve certainly heard all about it, but do you really know what it is? Pi is that pesky mathematical expression first used in 1706 that is the ratio of a circle’s circumference to its diameter, measured out as 3.14 (and, oh, so much more since the decimals never stop going, ever). This formula plays an integral part in math and engineering and has proven the most popular math aspect to move into pop culture, likely because it is easy to know and hard to understand. Math people love to celebrate their fame on 3/14. We will celebrate with them. Somehow.