rotate v. 旋转(rot+ate)
rotatory a. 旋转的;轮流的(rotate+ory)
rotor n. 旋转体(not+or)
rotund a. 圆形的;圆胖的(rot 转→圆+und→圆的,胖的)
rotundity n. 圆形;圆胖(rotund+ity)