In the mathematical community, March 14 is Day, the number that expresses the ratio of a circle’s circumference to its diameter. The one we always talked about in school: “π [or ] is equal to 3.14159 …”. But why March 14?

Unlike much of the rest of the world, in the United States, dates are written in the month/day/year format. So March 14 is 3/14. That’s why physicist Larry Shaw of San Francisco thought of celebrating Pi Day on that date. The celebration began gaining popularity and, in 2009, the U.S. House of Representatives officially declared March 14 as National Pi Day.

The word “pi” is a homophone of “pie”, as both are pronounced /paɪ/. This is why, in many places, it is celebrated by eating none other than pie! Some universities have different rituals, such as sending letters of acceptance (or rejection) to potential students on that particular day. Others also celebrate the birthday of Albert Einstein, who was born on March 14, 1879.

With regard to the written expression of the word “pi”, it should be written in lowercase. Numerical expressions are common nouns, and the correct way to write them is with lower case letters, unless they are part of the name of a , in which case, capital letters must be used in each of the nouns and adjectives that comprise it: National Pi Day.

We may be a little late this year; but, next year, we’ll already have an excuse ready to eat some pie.

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