Need a great gift for your favorite math teacher? Our pi symbol key chain may be the perfect thing. Our pi symbol was cast from alloy metal and it measures approximately 2 inches --(we wanted to make it 3.14159265 inches, but we thought it would be too big:) It hangs from a standard size steel key ring and it comes packaged in a nice box with a small blank card on it with the pi symbol, so that you can write a small thoughtful note.
The number π is a mathematical constant, the ratio of a circle's circumference to its diameter, approximately equal to 3.14159. It has been represented by the Greek letter "π" since the mid-18th century.