radius diameter and circumference

describe the relationship between them all

you have to use the diameter to find the circumference: pi x diameter.

the radius is half of the diameter.

the distance

The distance around a circle is called the circumference. The distance across a circle through the center is called the diameter. pi is the ratio of the circumference of a circle to the diameter. Thus, for any circle, if you divide the circumference by the diameter, you get a value close to pi.

radius

The radius of a circle is the distance from the center of a circle to any point on the circle. If you place two radii end-to-end in a circle, you would have the same length as one diameter. Thus, the diameter of a circle is twice as long as the radius.

diameter

The diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle.

circumference

Circumference is the linear distance around the edge of a closed curve or circular object.