let的过去式和过去分词是let,lets又是什么意思呢应该是“让”的意思吧,但是在词典里有查不到.eg.if he lets you go without a ticket.新概念第2册,第16课1.为什么不是if he let you...2.是不是所有的时态“让”,都可以用lets请举例说明.

第三人称单数形式呀

I think you mean "let" and "let's"
LET'S=LET US
LET as transitive verb: Inflected Form(s): letted or let; letting
LET as a noun:
1 : something that impedes : OBSTRUCTION
2 : a shot or point in racket games that does not count and must be replayed
LET as a verb:
Inflected form(s): let; letting
transitive senses
1 : to cause to : MAKE
2 a : to offer or grant for rent or lease b : to assign especially after bids
3 a : to give opportunity to or fail to prevent b -- used in the imperative to introduce a request or proposal c -- used as an auxiliary to express a warning
4 : to free from or as if from confinement
5 : to permit to enter, pass, or leave
6 : to make an adjustment to
intransitive senses
1 : to become rented or leased
2 : to become awarded to a contractor
synonym see HIRE
- let alone : to leave undisturbed also : to leave to oneself
- let fly : to hurl an object
- let go : to dismiss from employment
- let it all hang out : to reveal one's true feelings : act without dissimulation
- let one have it : to subject to vigorous assault
- let rip 1 : to utter or release without restraint 2 : to do or utter something without restraint
- let the cat out of the bag : to give away a secret

he是第三人称单数，所以后面的动词加S，别想得太复杂喇

第三人称单数一般现在时
简称“三单现”

lets在这里是第三人称单数形式,因为he是第三人称单数.要是主要非第三人称单数,则用let
1.eg.if he lets you go without a ticket
2.I let him go without a ticket

当动词前面的人称是第三人称单数时，一般现代时动词要加s。这一语法现象称为一般现代时第三人称单数。