- (anatomy) The long bone in the forearm, on the side of the thumb.
- (geometry) A line segment between any point on the circumference of a circle and its center/centre.
- (geometry) The length of this line segment.
Etymology:radiusLatin, radius, "ray".
- Dutch: straal
- German: Halbmesser , Radius
- Spanish: radio
- French: rayon
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