radius Meaning, Definition & Usage

  1. noun the length of a line segment between the center and circumference of a circle or sphere
    r.
  2. noun a straight line from the center to the perimeter of a circle (or from the center to the surface of a sphere)
  3. noun a circular region whose area is indicated by the length of its radius
    • they located it within a radius of 2 miles
  4. noun the outer and slightly shorter of the two bones of the human forearm
  5. noun support consisting of a radial member of a wheel joining the hub to the rim
    wheel spoke; spoke.

WordNet

Ra"di*us noun
Etymology
L., a staff, rod, spoke of a wheel, radius, ray. See Ray a divergent line.
Wordforms
plural L Radii E Radiuses
Definitions
  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. ✍ The radius is on the same side of the limb as the thumb, or pollex, and in man it 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. (b) Radiating organs, or color-markings, of the radiates.
  5. The movable limb of a sextant or other angular instrument. Knight.

Webster 1913