Radius: The distance from a circle’s center to its edge, the radius is generally represented with the variable “r”. Diameter: A straight line going through the center of circle with endpoints on the circle’s edge, a circle’s diameter is equal to twice its radius, given by the formula diameter = 2 · radius. [d = 2r] Circumference: The distance around the edge of a circle, a circle’s perimeter Circumference is found using the formula 2 · pi · radius [C = 2πr]
