Command Do this! Don’t do that! Suggestion Let’s do this!

Do this! Don’t do that! Let’s do this!

Use come/look/go/wait/be etc. when we tell somebody to do something:
command form: the infinitive (base form) of the verb:

Come in.
Please be quiet. I’m working.

Here are some orders you could give your pet dog:
Come here!
Sit!
Heel!
Fetch!

also (= I hope you have a good holiday etc.)
Have a good holiday!
Have a nice time!
Have a good flight!
Have fun!
‘Have a chocolate.’ ‘Oh, thanks.’
(= would you like a chocolate?)

Requests

You can also use the imperative to make a request, but you should use a polite word before the verb:
Please take a seat.
Please wait here.
Please hold the line.

In written English, you might also see “Kindly” used as a polite word:

Kindly return the documents as soon as possible.
Kindly forward this to the Sales and Marketing department.
Kindly send me 2 copies of your brochure.

Negative command: Don’t (= Do not) + V (inf.)…

… when we tell somebody not to do something:
Be careful! Don’t fall.
Be here on time. Don’t be late.
Please don’t smoke here.

Let’s

Let’s (= Let us) + V (inf.)…
… when you want people to do things with you, make a suggestion.

Let’s = Let us. It’s a nice day. Let’s go out.
(= you and I can go out)

Shall we go out tonight?
No, I’m tired. Let’s stay at home.

The negative is Let’s not… It’s cold. Let’s not go out. Let’s stay at home.

Compare

Ran, and you will catch the bus.
Ran, or you will catch the bus.

Imperative with and

We can sometimes use the imperative + and instead of an if-clause, for example:
Go now and I’ll never speak to you again. (If you go now, I’ll never speak…)

Imperative with do

If we put do before the imperative the effect is to make requests, apologies and complaints more emphatic but also more polite:

Do take a seat. (request)
Do forgive me. I didn’t mean to offend you. (apology)
Do try to keep the noise down, gentlemen. (complaint)

Imperative with always, never, ever

The words always, never, ever come before imperatives, as in:
Always remember who’s boss.
Never speak to me like that again.
Don’t ever speak to me like that again.

Passive imperative

We sometimes make passive imperatives with get,
for example:
Get vaccinated before your holiday.

Imperative with question tag

We sometimes use these question tags after imperatives: can you? can’t you? could you? will you? won’t you? would you?
Look at these examples:
Lend me a dollar, can you?
Help me with this, will you?
Keep still, won’t you?