Definition:Radius


 * Geometry:
 * Radius of a Circle: a straight line segment whose endpoints are the center and the circumference of the circle.
 * Radius of a Sphere: a straight line segment whose endpoints are the center and the surface of the sphere.


 * Analytic Geometry:
 * The radial coordinate of a point $P$ in a system of polar coordinates is also known as the radius of $P$.
 * Radius of Curvature|: the reciprocal of the absolute value of its curvature
 * Radius Vector


 * Topology and Metric Spaces:
 * Radius of an $\epsilon$-Ball: In the open $\epsilon$-ball $B_\epsilon \left({x}\right)$ of the point $x$, the value $\epsilon$ is its radius.


 * Analysis:
 * Radius of Convergence: The distance from the endpoints to the midpoint of the interval on which a power series is convergent.


 * Graph Theory:
 * Radius of graph


 * Mechanics:
 * Radius of gyration

Also see

 * Definition:Diameter
 * Definition:Circumference