track (for trains etc.); orbit (of a satellite); (fig.) a person's established path in life; desired trajectory (of a business or other endeavor); (audio engineering) track; (quantum mechanics) orbital

to be derailed; to go off the rails; (fig.) to overstep the bounds; (fig.) to have an extramarital affair

the right track

rail; railroad track

locus; orbit; trajectory; track

errant

light rail; transit system (underground, at street level or elevated); streetcar; metro (abbr. for 轻型轨道交通)

to run off the track; to step out of line; to overstep the bounds of propriety