ra|di|us

ra|di|us «RAY dee uhs», noun, plural -di|i or -di|us|es.

1. any line going straight from the center to the outside of a circle or sphere. Any spoke in a wheel is a radius.

2. a circular area measured by the length of its radius: »

The explosion could be heard within a radius of ten miles.

3. a) the distance an airplane, ship, or other vehicle can travel and still have enough fuel to return: »

a submarine with a cruising radius of 4,000 miles.

b) Figurative. the field of operation or range of influence of anything: »

the radius of Western culture.

4. a) that one of the two bones of the forearm, which is on the thumb side. b) a corresponding bone in the forelimb of other vertebrates.

5. a line thought of as dividing an animal having radial symmetry into like parts.

6. the distance between the center and the axis of rotation in an eccentric; eccentricity.

╂[< Latin radius ray, spoke of a wheel, radius bone. See etym. of doublet ray¹. (Cf. ↑ray)]