Definition of radius
1
: a line segment extending from the center of a circle or sphere to the circumference or bounding surface
2a
: the bone on the thumb side of the human forearm
also
: a corresponding part of vertebrates above fishes
b
: the third and usually largest vein of an insect's wing
3a
: the length of a radius
a truck with a short turning radius
b
: the circular area defined by a stated radius
c
: a bounded or circumscribed area
4
: a radial part
5
: the distance from a center line or point to an axis of rotation
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Merriam-Webster unabridged
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Time Traveler for radius
The first known use of radius was in 1578
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