Main Entry: ra·di·us

Pronunciation: \ˈrā-dē-əs\

Function: noun

Inflected Form(s): plural ra·dii \-dē-ˌī\ also ra·di·us·es

Etymology: Latin, ray, radius

Date: circa 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 usually largest vein of an insect's wing
3 a : the length of a radius <a truck with a short turning radius> 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