- [noun] the length of a line segment between the center and circumference of a circle or sphere
- [noun] a straight line from the center to the perimeter of a circle (or from the center to the surface of a sphere)
- [noun] a circular region whose area is indicated by the length of its radius; "they located it within a radius of 2 miles"
- [noun] the outer and slightly shorter of the two bones of the human forearm
- [noun] support consisting of a radial member of a wheel joining the hub to the rim