RADIUS

:For other senses of this word, see radius (disambiguation).

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In classical geometry, a radius of a circle or sphere is any line segment with one endpoint on the circle (i.e., the circular boundary) and the other at the center of the circle. By extension, the radius of a circle or sphere is the length of any such segment. The radius is half the diameter.

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More generally — in geometry, engineering, graph theory, and many other contexts — the radius of something (e.g., a cylinder, a graph, or a mechanical part) is the distance from its center or axis to its outermost points. See also diameter.

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Geometry: Geometry (Greek Γεωμετρια, geo = earth, metria = measure) arose as the field of knowledge dealing with spatial relationships. It was one of the two fields of pre-modern mathematics, the other being the study of numbers. In modern times, geometric c...

Circle: :See The Circle for the distributed file storage system, and see ring (diacritic) for the diacritic mark....

Sphere: :For other uses, see sphere (disambiguation)....