(n): the linear extent in space from one end to the other; the longest dimension of something that is fixed in place
(n): a straight line from the center to the perimeter of a circle (or from the center to the surface of a sphere)
(n): a line traced by a point traveling in a constant direction; a line of zero curvature
(n): a circular region whose area is indicated by the length of its radius
(n): the extended spatial location of something
(n): the outer and slightly shorter of the two bones of the human forearm
(n): a bone in the arm
(n): support consisting of a radial member of a wheel joining the hub to the rim
(n): any device that bears the weight of another thing
(And a bone!)
"Zool. and Palaeontol. (a) The bony spine or sting near the base of the tail of a stingray; (b) the alveolus of a belemnite; (c) the dorsal fin of a fish (cf. sense 3f). Obs. rare." (OED)