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radius definition

ra·dius (dē əs)

noun pl. radii -·dii′ (-ī′) or radiuses -·uses

  1. a raylike or radial part, as a spoke of a wheel
    1. any straight line extending from the center to the periphery of a circle or sphere
    2. the length of such a line
    1. the circular area or distance limited by the sweep of such a line no house within a radius of five miles
    2. the distance a ship or airplane can travel and still return to its point of origin without refueling
  2. an extent, scope, range, etc. of a limited or specified kind within the radius of one's experience
    1. the shorter and thicker of the two bones of the forearm on the same side as the thumb
    2. a corresponding bone of the forelimb of a four-legged animal
  3. Zool.
    1. any of the planes of division of the body of a radially symmetrical animal
    2. any of various longitudinal veins in the wing of an insect

Etymology: L, rod, spoke (of a wheel), hence radius, ray (of light), ? akin to radix, root

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