[] a small device that you press or move up and down in order to turn a light or piece of electrical equipment on and off（电路的）开关，闸，转换器◆the on-off switch通断开关a change from one thing to another, especially when this is sudden and complete（尤指突然彻底的）改变，转变◆I've decided to make the switch from full-time to part-time work.我已决定从全职工作改为兼职工作。◆a switch in/of policy政策的改变◆a policy switch政策转变bait-and-switch