Definition:Sphere/Geometry/Radius

From ProofWiki
Jump to navigation Jump to search

This page is about the radius of a sphere. For other uses, see Definition:Radius.

Definition

A radius of a sphere is a straight line segment whose endpoints are the center and the surface of the sphere.

The radius of a sphere is the length of one such radius.


Linguistic Note

The plural of radius is radii, pronounced ray-dee-eye.

This irregular plural form stems from the Latin origin of the word radius, meaning ray.

The ugly incorrect form radiuses can apparently be found, but rarely in a mathematical context.