The **radius** of a [[Circle|circle]] may refer to any [[Line, Line-Segment, Ray|line-segment]] with one endpoint on the circle and another endpoint at the center of the circle, or it may just refer to the length of one of these segments The **radius** of a [[regular polygon]] is typically the radius of the circle containing its vertices. (The radius of the circle tangent to all sides is the [[‡ Apothem]]