Definition of radii:
(n) :
(geometry) A line segment between any point of a circle or sphere and its center.
(n) :
(geometry) The length of this line segment.
(n) :
(anatomy) The long bone in the forearm, on the side of the thumb.
(n) :
(zoology) The lighter bone (or fused portion of bone) in the forelimb of an animal.
(n) :
Anything resembling a radius, such as the spoke of a wheel, the movable arm of a sextant, or one of the radiating lines of a spider's web.
(n) :
(entomology) One of the major veins of the insect wing, between the subcosta and the media; the vein running along the costal edge of the discal cell.