The number *π* is a mathematical constant, represented by the 16th letter of the Greek alphabet "*π*" since the mid-18th century, and is spelled out as "Pi". It is also referred to as **Archimedes' constant**.

**Pi is the number you get when you divide the circumference of a circle by its diameter. **

Pi is an important number used in many different areas of mathematics and geometry. Pi is used in most calculations for building and construction, quantum physics, communications, music theory, medical procedures, air travel, and space flight, to name a few.