allow 普通用词，侧重听任、默许或不加阻止。在正式场合可用来表客气的请求。
let 常用词，用于各种非正式场合，语气最弱，指允许或无力阻止某事，暗示漠不关心或听之任之。
permit 正式用词，在多数场合可与allow换用，语义最强，指准许某人做某事，含权威或正式的意味。
leave 侧重不加干涉。
authorize 语气最强，指权威性的允许与认可。
参考例句
1. Let him tell you what has happened. 让他告诉你发生了什么事情。
2. To let you know we are family. 让你们知道，我们是一家人唷。
3. Let me try this skirt on alone. 让我独自试穿一下这件裙子。
英英解释
n.
1. the most brutal terrorist group active in Kashmir; fights against India with the goal of restoring I
2. a serve that strikes the net before falling into the receiver's court; the ball must be served again v.
1. make it possible through a specific action or lack of action for something to happen
2. actively cause something to happen
3. consent to, give permission
4. cause to move; cause to be in a certain position or condition
5. leave unchanged
6. grant use or occupation of under a term of contract
