The distance from the center of a Circle to its Perimeter, or from the center of a Sphere
to its surface. The radius is equal to half the Diameter.

*See also *Bertrand's Problem, Circle, Circumference, Diameter, Extent, Inversion Radius,
Kinney's Set, Pi, Radius of Convergence, Radius of Curvature, Radius (Graph), Radius
of Gyration, Radius of Torsion, Radius Vector, Sphere

© 1996-9 *Eric W. Weisstein *

1999-05-25