[ra.di.us] n, pl ra.dii also ra.di.us.es [L, ray, radius] (ca. 1611) 1: a line segment extending from the center of a circle or sphere to the circumference or bounding surface
2. a: the bone on the thumb side of the human forearm; also: a corresponding part of vertebrates above fishes b: the third and usu. largest vein of an insect's wing 3 a: the length of a radius "a truck with a short turning ~" b: the circular area defined by a stated radius c: a bounded or circumscribed area
4: a radial part
5: the distance from a center line or point to an axis of rotation