Let習慣用語
       
         let alone, means not to mention; much less.是指更不用提；更别说的意思。例如：

　　Their ancestors had been dirt poor and never saw royalty, let alone hung around with them?

　　“他们的祖先穷得要命，从来没有见过王族成员，更不用说和他们在一起了”。

　　let go, means to cease to employ; dismiss.是指不再雇用；解雇的意思。例如：

　　had to let 20 workers go.

　　必须解雇二十名工人。

　　let off on, means to cause to diminish, as in pressure; ease up on.是指降低，如压力；缓和的意思。例如：

　　Let off on the gas so that we do not exceed the speed limit.

　　减小油门以防止超过限速。

　　let (one's) hair down, means to drop one's reserve or inhibitions.是指消除某人的拘谨或压抑的意思。