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, -di⋅us⋅es. | 1. | 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. |
| 2. | the length of such a line. |
| 3. | any radial or radiating part. |
| 4. | 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. |
| 5. | a field or range of operation or influence. |
| 6. | extent of possible operation, travel, etc., as under a single supply of fuel: the flying radius of an airplane. |
| 7. | Anatomy. the bone of the forearm on the thumb side. Compare ulna (def. 1). |
| 8. | Zoology. a corresponding bone in the forelimb of other vertebrates. |
| 9. | Machinery Now Rare. the throw of an eccentric wheel or cam. |
| 10. | a rounded corner or edge on a machined or cast piece of metal. |
| 11. | Entomology. one of the principal longitudinal veins in the anterior portion of the wing of an insect. |
ra·di·i (rā'dē-ī') n. A plural of radius. |
radius ra·di·us (rā'dē-əs)
n. pl. ra·di·us·es or ra·di·i (-dē-ī')
A line segment that joins the center of a circle with any point on its circumference.
A long, prismatic, slightly curved bone, the shorter and thicker of the two forearm bones, located laterally to the ulna.
| radius (rā'dē-əs) Pronunciation Key
Plural radii (rā'dē-ī') or radiuses
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