a straight line extending from the center of a circle or sphere to the circumference or surface

The radius of a circle is half the diameter.

the length of such a line.

any radial or radiating part.

a circular area having an extent determined by the length of the radius from a given or specified central point

every house within a radius of 50 miles.

a field or range of operation or influence.

extent of possible operation, travel, etc., as under a single supply of fuel

the flying radius of an airplane.

Anatomy . the bone of the forearm on the thumb side. Compare ulna ( def. 1 ) .

Zoology . a corresponding bone in the forelimb of other vertebrates.

Machinery Now Rare . the throw of an eccentric wheel or cam.

a rounded corner or edge on a machined or cast piece of metal.

Entomology . one of the principal longitudinal veins in the anterior portion of the wing of an insect.

noun

ambit , boundary , compass , expanse , extension , extent , interval , limit , orbit , purview , reach , semidiameter , space , span , spokenotes:the radius is the outer arm bone and the ulna is the inner , longer arm bone , field , line , range , spoke , sweep