"radii" in the noun sense
1. radius, r
the length of a line segment between the center and circumference of a circle or sphere
a straight line from the center to the perimeter of a circle (or from the center to the surface of a sphere)
a circular region whose area is indicated by the length of its radius
"they located it within a radius of 2 miles"
the outer and slightly shorter of the two bones of the human forearm
5. spoke, wheel spoke, radius
support consisting of a radial member of a wheel joining the hub to the rim
Source: WordNet® (An amazing lexical database of English)
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