Circumference of a Circle
The circumference of a circle is the distance all the way around the circle. It's the same as the perimeter, but a special word that we only use for the perimeter of a circle. The circumference is always equal to twice the radius of the circle times π (pi), or 2πr.
Learn by doing: figure out the circumference of a plate in your kitchen.
Area of a Circle
More about Geometry