The radius is the distance from the center of a circle or sphere to any point on its circumference or surface.
Diameter: The diameter is twice the length of the radius, and it goes straight through the center of a circle or sphere.
Circumference: The circumference is the distance around a circle, which can be found by multiplying 2π by the radius.
Surface Area: The surface area of a sphere can be calculated using 4π times the square of its radius.