Definition of radius

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