radius

noun (plural radii /ˈrādēˌī/ or radiuses)

• 1a straight line from the center to the circumference of a circle or sphere. See also illustration at geometric.
• a radial line from the focus to any point of a curve.
• the length of the radius of a circle or sphere.
• a specified distance from a center in all directions:there are plenty of local pubs within a two-mile radius

• 2 Anatomy the thicker and shorter of the two bones in the human forearm. Compare with ulna.
• Zoology the corresponding bone in a vertebrate’s foreleg or a bird’s wing.
• Zoology (in an echinoderm or coelenterate) any of the primary axes of radial symmetry.
• Entomology any of the main veins in an insect’s wing.