the thicker and shorter of the two bones in the human forearm.
Merriam-Webster Online Dictionary
radius (noun)1.
a line segment extending from the center of a circle or sphere to the circumference or bounding surface
2.
a) 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
3.
a) 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 part - radial
5.
the distance from a center line or point to an axis of rotation