the length of a line segment between the center and circumference of a circle or sphere
同义词：r
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 forearmsupport consisting of a radial member of a wheel joining the hub to the rim