There are three measures that can be taken to better under the nature of a circle. You can determine the linear distance that is covered by the circle itself that measure is called the circumference of the circle. If you were to draw a straight line through the center of the circle and touch each end of the circle this distance is called the diameter. The distance from anywhere on a circle to the middle is called the radius of the circle. A Pi symbol as a visual symbol that encompasses the ratio of the circumference of a circle to that of its diameter. The Pi symbol is also the sixteenth letter of the Greek alphabet. Since it is a ratio it does not matter how large of a circle you have, it is always set to the same ratio. Pi can be used to learn much more information about a circle, if you have only a few measures of the circle. The ratio converts to 3.14 (followed by a repeating decimal.)

On March fourteenth every year many math teachers tend to recognize this day as Pi Day (Math 14th = 3/14). See the irony in the date that Pi Day is celebrated on? The idea for the celebration was developed by a test preparation company. It gained steam in the math teacher community and is a staple at most high schools.