Meaning of “let” - Learner’s Dictionary

let

verb [ T ] us uk /let/ present participle letting, past tense and past participle let
Extra Examples
We can't let a mistake like this happen again.Don't let me keep you from your work.We don't usually let students take books home.She wouldn't let us watch TV.I tried to help her, but she wouldn't let me.
ALLOW

B1 to allow someone to do something, or to allow something to happen:

Let them play outside.
Don't let the camera get wet.
It's best to let nature take its course.
We let a whole year go by before we tried again.
let sb/sth in/past/through, etc

B2 to allow someone or something to move to a particular place:

They won't let us past the gate.
I won't let him near my children.
The roof lets in a lot of rain.
let's

A2 something that you say when you are making a suggestion:

Let's eat out tonight.
Let's not bother with the washing-up.
let me/us

something that you say when you are offering to help someone:

Let me carry your cases.
BUILDING

If you let a building or part of a building, you allow someone to live there and they give you money:

I let the top floor of my house to a student.
Let's see/Let me see

something that you say when you are trying to remember something or calculate something:

Let's see - there are five people and only three beds.
It must have been - let me see - three years ago.
Let's say

something that you say when you are suggesting a possible situation or action:

Let's say you manage to sell half the books.
Let's say we'll meet back here in an hour.
let sb know (sth)

A2 to tell someone something:

[ + question word ] I'll let you know when we've fixed a date for the meeting.
let (sth) go

to stop holding something:

I let go of the rope.
You have to let the handle go.
let yourself go

to allow yourself to become less attractive or healthy:

It's easy to let yourself go when you're pregnant.

to relax completely and enjoy yourself:

It's a party - let yourself go!
let's face it

something that you say when the truth is unpleasant but must be accepted:

Let's face it, we're not getting any younger.

(Definition of “let” from the Cambridge Learner’s Dictionary © Cambridge University Press)