Pi (π) is the ratio of a circle’s circumference to its diameter. Pi is a constant number, meaning that for all circles of any size, it will be the same.
Pi has it's first beginnings thousands of years ago. From the ancient Babylonians, Egyptians and Greeks, Pi is a calculation refining the area of a circle. Through the use of thousands of polygons and their respective areas, scientists and mathematicians have been refining this number beginning with the Babylonians 4000 years ago with 3.16 until its present day calculation of 3.14 etc. by Archimedes, who noted this is still an estimate.
The symbol for "pi" that we recognize today was introduced by William Jones in 1706. In 1737 the symbol became a popular mainstay by Leonard Euler.
While Pi Day is a great way to celebrate math, science and of course, pie - there's a long history behind the number that is still known only an approximation, rather than an exact calculation.
READ MORE ABOUT THE HISTORY OF PI HERE