1.半径（长度）
2.半径范围，周围
3.桡骨
词形变化
- 复数 radii
- the outer and slightly shorter of the two bones of the human forearm
- a circular region whose area is indicated by the length of its radius
- a straight line from the center to the perimeter of a circle (or from the center to the surface of a sphere)
- support consisting of a radial member of a wheel joining the hub to the rim
- the length of a line segment between the center and circumference of a circle or sphere