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