Where Did The Word”Pi” Come From? Getty Where is the word pi from? Pi is the Latin name of the sixteenth Greek letter, π. (Mathematic notation borrows from a multitude of alphabets and typefaces.) The first recorded use of π as a mathematical symbol comes from the Welsh mathematician William Jones in a 1706 work called Synopsis Palmariorum Matheseos, in which he abbreviated the Greek περιϕέρεια, (meaning “circumference,” or “periphery”) to its first letter: π. What does pi mean in mathematics? The mathematical pi is defined as “the ratio of the circumference of a circle to its diameter.” It’s also known as Archimedes’ Constant, after the ancient Greek mathematician of the same name, who, in addition to coming up with an algorithm for calculating pi, also invented an early type of irrigation pump called the Archimedian screw. Very medieval-sounding, but we digress. What makes pi so magical is that it doesn’t matter how big or small the circle may be: the pi ratio remains the same. Pi is what’s known as an irrational number, which means, in part, that “it can never terminate or repeat when written out in decimal form.” As far as we can tell, it goes on forever, which is a bit mind-boggling. Computers have calculated pi to decimal places in the trillions. It is also a transcendental number, a concept that exceeds the scope of this post but believe us it’s very cool. What is Pi Day? Pi Day is the March 14th holiday commemorating the mathematical constant π (pi), written numerically as 3.141592+, and pronounced “pie.” And yes: lots of people mark the occasion by eating pie because why would you pass up an occasion to eat pie? World record pi? Memorizing as many digits of pi as possible has become an obsession for many. The Guinness World Record for memorizing digits of π is held by a man named Lu Chao, who set the record in November 2005 in the Shaanxi province of China. It took him 24 hours and 4 minutes to recite the 67,890th decimal place of π without a mistake. Kind of makes us feel inadequate for all the times we’ve forgotten our 4-digit PIN.