Photo: Getty Images

You keep hearing people say “Happy Pi Day!” — which you know is spelled without the ‘i’ for some reason — and you’re more than happy to take advantage of the dessert deals around town today, but you can’t help but wonder, why is Pi Day celebrated on March 14th?

You don’t want to ask your friends who seem to take today really seriously. They majored in math or physics or maybe even computer science and you can’t help but feel something got lost in translation when you went, instead, into the humanities. We get it; we’re writers.

So to help you out, here’s a quick breakdown, let’s call it Pi Day for Poets, and we’ll answer the nagging question why is Pi Day celebrated on March 14th.

## What is Pi Day, anyway?

Pi Day is, quite simply, a quirky holiday that celebrates the mathematical symbol pi (π). It’s also a good excuse to eat pie. After all, when else do you get to do that, other than Thanksgiving?

But if you don’t quite get the particular appeal of pi, we’ll try to explain. This tiny little symbol represents a lot in just one character. It represents the ratio, or relationship, between a circle’s circumference (distance around the outside) to its diameter (the distance straight through from one side to the other). And it does this for any circle, no matter the size. So this relationship in measurements can be expressed through one tiny symbol in a circle as big as a planet or as small as a pencil eraser.

## So, why is Pi Day celebrated on March 14th?

Even though that tiny, elegant symbol represents a relationship, it can also be expressed through numbers. Well, sort of. It’s an irrational number, meaning its exact value is unknowable. You might have seen people trying to list of a very long string of seemingly random numbers starting with 3.14 — that’s what we’re talking about. The numbers in pi could keep going forever; they’re infinite.

Daniel Tammet, pictured above, holds the European record for reciting pi from memory to 22,514 digits in five hours and nine minutes.

But even though we have figured out the value of pi out to many places past the decimal point, you’ll most often hear it summarized by this much smaller number: 3.14. That’s your answer to why is Pi Day celebrated on March 14th. March 14th can be written out in multiple ways, including 3/14 and 3.14, which mirrors those first three digits of pi.

But it’s fine if you just use the day as an excuse to enjoy a slice of apple pie. Just don’t forget to make it a la mode.