Radius

: radii or radiuses)[a] of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length.

The radius of a regular polygon is the line segment or distance from its center to any of its vertices.

The name comes from the Latin radius, meaning ray but also the spoke of a chariot wheel.

In either case, the radius may be more than half the diameter, which is usually defined as the maximum distance between any two points of the figure.

The inradius of a geometric figure is usually the radius of the largest circle or sphere contained in it.

The radius of a d-dimensional hypercube with side s is The polar coordinate system is a two-dimensional coordinate system in which each point on a plane is determined by a distance from a fixed point and an angle from a fixed direction.

[8] In a spherical coordinate system, the radius describes the distance of a point from a fixed origin.