Let (verb)

1. Allow something to happen or be done.
2. Rent out.
3. Give a chance to.
4. Prevent from.

Origin:

Middle english 'leten' from old english 'lǣtan' meaning to allow, let, from germanic 'lētaną' meaning to allow.

Examples:

1. Let's go!
2. I'll let you know.
3. Let him go.
4. She let the cat out.
5. They let the contract.