a right line drawn or extending from the center of a circle to the periphery; the semidiameter of a circle or sphere.-the preaxial bone of the forearm, or brachium, corresponding to the tibia of the hind limb. see illust. of artiodactyla.-a ray, or outer floret, of the capitulum of such plants as the sunflower and the daisy. see ray, 2.-the barbs of a perfect feather.-radiating organs, or color-markings, of the radiates.-the movable limb of a sextant or other angular instrument.