let alone, means not to mention; much less.是指更不用提；更別說的意思。例如：
their ancestors had been dirt poor and never saw royalty, let alone hung around with them?
“他們的祖先窮得要命，從來沒有見過王族成員，更不用說和他們在一起了”。
let go, means to cease to employ; dismiss.是指不再雇用；解僱的意思。例如：
had to let 20 workers go.
必須解僱二十名工人。
let off on, means to cause to diminish, as in pressure; ease up on.是指降低，如壓力；緩和的意思。例如：
let off on the gas so that we do not exceed the speed limit.
減小油門以防止超過限速。
let (one's) hair down, means to drop one's reserve or inhibitions.是指消除某人的拘謹或壓抑的意思。
let up on, means to be or become more lenient with.是指較寬容地對待的意思。例如：
why don't you let up on the poor child?
你為什麼不能較寬容地對待這個可憐的孩子呢?
let's，這是我們最常用的。通常表示建議或命令。例如：
let's go swimming on sunday.
我們星期日去游泳吧！
come on mary, let's dance!
來吧！瑪麗，我們來跳舞吧！
let the cat out of the bag，是指在不小心的情況下瀉露了秘密的意思。