# What is a radius ? Definition and examples.

## Radius of a circle

The radius of a circle is any line segment from the center of the circle to a point on the circle.

The radius of a circle can also refer to the distance between the center of the circle and any point on the circle. Below, we show the radius with a green segment.

## Radius of a sphere

The radius of a sphere is any line segment from the center of the sphere to a point on the sphere.

The radius of a sphere can also refer to the distance between the center of the sphere and any point on the sphere. Below, we show the radius with a green segment.

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