Why Pi

Why do we call it "pi" and not some other Greek letter?  Well, according to this article, "How a farm boy from Wales gave the world pi", we owe it to William Jones who published the popular book "Synopsis palmariorum matheseos" which was sort of a primer on the current state of mathematics in the early 1700s.


This book contains the first recorded use of the symbol pi to represent ratio of a circle's circumference to its diameter (page 263).   It's believed he chose this as it was the first letter in the Greek word for perimeter or periphery.

When I asked the kids to guess when it was first used, they had a bunch of wild guesses ranging from 1000 BC to 400 AD, but nothing near as recently as the early 1700s.   I must admit, I was surprised to learn it was so late as well.  I guess you never know.