pl. radii [L. radius, staff, spoke, ray]
1. A line extending from the center point of a circle to its circumference.
2. The more lateral and shorter bone of the forearm. It revolves partially about the ulna. Its head articulates with the capitulum of the humerus and with the radial notch on the ulna and is encircled by the annular ligament. Its lower portion articulates with the ulna by the ulnar notch, and by another articulation with the navicular (scaphoid) and lunate bones of the wrist.
radial (rād′ē-ăl), adj.
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