軌道
track（電車）;rail（鐵路）;orbit（衛(wèi)星）;parabolic orbit（拋物線）;trajectory(射體、彈道)
火車出了～。The train has been derailed./五年計(jì)劃上～。The Five-Year Plan is well under way./生產(chǎn)已走上～。Production has got on the right track./把衛(wèi)星送入～put a satellite into orbit/繞月～ lunar orbit/雙～double track; two-track/～車motor-trolley /～空間站orbital space station