Pi (Greek letter "I") is the symbol used in mathematics to represent a constant - the ratio of the circumference of a circle to its diameter - which is approximately 3.14159.
Pi Day was first recognised 30 years ago back in 1988 by physicist Larry Shaw, according to Google. Because Pi is a mathematical constant it remains unchanged by the size of the numbers it's used to equate and its digits never repeat.
The value of pi is 22/7 and today even school children use the value to calculate the circumference and area of a circle by substituting the value of pi in the formulas.
As we celebrate again in 2018, here are some Pi Day facts you should know. On the other, food lovers see the day as an excuse to bake pies, which is both ingenious and delicious-and lucrative for food brands like Genius Kitchen (see our recipe for Surprise Rainbow Pi Day Cake).
The award-winning pastry chef created the doodle using actual caramel apple pies. It was however, William Jones, a mathematician from Wales, who first gave the Greek letter its current mathematical definition. Interestingly, Albert Einstein's birth anniversary falls on March 14, which is also celebrated at Princeton by organising an annual Einstein look-alike contest.
Pi is also a source of inspiration for competitions, where participants have to recite as many decimals of the number as possible. For instance, there are astounding formulae in which smaller and smaller numbers add up to pi and one of the earliest such infinite series to be discovered says that pi equals four times the sum 1 - 1⁄3 + 1⁄5 - 1⁄7 + 1⁄9 - 1⁄11 + ⋯.