radius

n.

  1. A right line drawn or extending from the center of a circle to the periphery; the semidiameter of a circle or sphere.
  2. The preaxial bone of the forearm, or brachium, corresponding to the tibia of the hind limb. See Illust. of Artiodactyla.
  3. A ray, or outer floret, of the capitulum of such plants as the sunflower and the daisy. See Ray, 2.
  4. The barbs of a perfect feather.
  5. Radiating organs, or color-markings, of the radiates.
  6. The movable limb of a sextant or other angular instrument.