Pi (π) is a special number that is used to find the circumference (perimeter) of a circle. A circle is like a cookie, and the circumference is the distance around the edge of the cookie.

The number pi is always the same for all circles, no matter how big or small the circle is. Pi is an irrational number, which means it goes on forever after the decimal point and never repeats. So, we often use the first few digits of pi, like 3.14, to find the circumference of a circle.

When you use pi to find the circumference of a circle, you multiply the diameter of the circle by pi. The diameter is the distance from one side of the circle to the other through the center of the circle. The result is the circumference of the circle, which is a measure of the distance around the edge of the circle.

So, pi is a very important number in mathematics and is used in many different ways to find measurements for circles and other shapes.