Ra"di*us (rā"d&ibreve;*ŭs), n.; pl. L. Radii (- ī); E.
Radiuses (-ŭs*&ebreve;z). [L., a staff, rod, spoke of a wheel, radius, ray. See Ray a divergent line.]
1. (Geom.) A right line drawn or extending from the center of a circle to the
periphery; the semidiameter of a circle or sphere.
2. (Anat.)
The preaxial bone of the forearm, or brachium, corresponding to the tibia of
the hind limb. See Illust. of Artiodactyla.
&fist; The radius is on
the same side of the limb as the thumb, or pollex, and in man it is so articulated that its lower end
is capable of partial rotation about the ulna.
3.
(Bot.) A ray, or outer
floret, of the capitulum of such plants as the sunflower and the daisy. See Ray, 2.
4. pl. (Zoöl.)
(a) The barbs
of a perfect feather.
(b) Radiating organs, or color-markings, of the radiates.
5. The movable limb of a sextant
or other angular instrument.
Knight.
Radius bar (Mach.),
a bar pivoted at one end, about which it swings, and having its other end attached to a piece which it causes to move in a circular arc. -- Radius of curvature. See under Curvature.
Hear it pronounced