释义：辐射光线；径向射线；半径；半径范围 双语释义：n.(名词)[C]半径(距离） (length of a) straight line from the centre of a circle or sphere to any point on its circumference or surface[C]用半径度量的圆形面积；半径范围 circular area measured by its radius英英释义： radiusn.the length of a line segment betwe