radius

radius [rā′dē əs]

n.

pl. radii [rā′dēī΄] or radiuses [L, rod, spoke (of a wheel), hence radius, ray (of light), ? akin to radix,ROOT¹]

1. a raylike or radial part, as a spoke of a wheel

2.

a) any straight line extending from the center to the periphery of a circle or sphere: see CIRCLE

b) the length of such a line

3.

a) the circular area or distance limited by the sweep of such a line [no house within a radius of five miles]

b) the distance a ship or airplane can travel and still return to its point of origin without refueling

4. an extent, scope, range, etc. of a limited or specified kind [within the radius of one's experience]

5.

a) the shorter and thicker of the two bones of the forearm on the same side as the thumb: see SKELETON

b) a corresponding bone of the forelimb of a four-legged animal

6. Zool.

a) any of the planes of division of the body of a radially symmetrical animal

b) any of various longitudinal veins in the wing of an insect