
- Pi | Definition, Symbol, Number, & Facts | Britannica- Oct 21, 2025 · pi, in mathematics, the ratio of the circumference of a circle to its diameter. The symbol π was devised by British mathematician William Jones in 1706 to represent the ratio … 
- Pi - Wikipedia- The number π (/ paɪ / ⓘ; spelled out as pi) is a mathematical constant, approximately equal to 3.14159, that is the ratio of a circle 's circumference to its diameter. 
- Pi - Math is Fun- Draw a circle with a diameter (all the way across the circle) of 1. Then the circumference (all the way around the circle) is 3.14159265... a number known as Pi. Pi (pronounced like "pie") is … 
- What Is Pi (π) in Math? A Kid-Friendly Definition- Pi (π) is a special number that tells us how the distance around a circle (its circumference) compares to the distance across the circle (its diameter). No matter the size of the circle, the … 
- What Is Pi, and How Did It Originate? - Scientific American- May 17, 1999 · Succinctly, pi—which is written as the Greek letter for p, or π—is the ratio of the circumference of any circle to the diameter of that circle. 
- What is Pi? - Pi Day- Pi (often represented by the lower-case Greek letter π), one of the most well-known mathematical constants, is the ratio of a circle’s circumference to its diameter. For any circle, the distance … 
- What Is Pi? Understanding the Number & Symbol - Statistics by Jim- What is pi in math terms? In math, pi is the ratio of a circle’s circumference to its diameter. π is an irrational, infinite decimal often written as 3.14159. 
- Pi - Math.net- Pi is a constant value. That is, the ratio of the circumference to the diameter is the same for all circles. The drawing below shows the circumference of a circle that has been "straightened … 
- What is Pi (π)? Definition, Formula, and Uses Explained- Pi, represented by the Greek letter π, is the ratio of the circumference of a circle to its diameter. It is a mathematical constant with the value equal to 3.14159. 
- What Is Pi, and Why Is It So Important? - ExtremeTech- Jan 25, 2025 · Pi, a mathematical constant denoted by the Greek letter π, is the ratio of a circle's circumference C to its diameter d: π = C/d.