► The second person: bare infinitive
We can express commands in English by an imperative sentence made with the bare infinitive without to.
Examples: Be careful. Open your books. Come here.
For the negative form we use do not or don't.
Don't be late. Do not sit down. Don't have so many bags.
We can mention a person in the command, usually at the end of the sentence.
Have something to eat, Greg.
If we talk to more people, we use the pronoun you to make the distinction between them.
You take these bags and you park the car. You wait here and I'll call the police.
► The emphatic imperative: do
In writing it is not usual to use an exclamation mark. If we put it at the end of an imperative sentence, it becomes more urgent.
Examples: Wait! Don't do that!
We can emphasize our request with do. It is common in polite requests.
Do sit down. Do be reasonable.
On the other hand, do before the imperative can express the irritation of the speaker.
Do be quiet. Do come on time.
You before the command also shows the speaker's anger or even rudeness.
You get out of here. Don't you follow me.
In a different context, however, it can show your positive emotions.
Don't you be so sad.
► The first person: let me, let us
In the first person we make it with let + me or let + us.
Examples: Let me do it for you. Let me see. - Let us go. Let's do some exercises.
For the negative we put not before the imperative.
Let us not be worried.
In spoken English it is possible to use don't at the beginning of imperative sentences.
Don't let's be worried.
► The third person: let him
We make it with let + him/her/it/them and the infinitive without to.
Examples: Let him go. Let her explain it. Let it be. Let them try it. Let the customers pay immediately.
This form is not very common in modern English. It is more usual to say the same in a different way.
He must go. She should explain it. Leave it alone. They can try it. The customers must pay immediately.
The negative form in the third person is archaic. We use more common forms instead.
They mustn't stay here. Mary is not to travel alone.
► The polite requests: shall, will
We can make a polite request in English if we put shall we or will you at the end of the imperative sentence. This is used in positive sentences.
Examples: Let's get started, shall we? Be careful, will you?
If you want to be even more polite, you can use questions instead of commands.
Will you pass me the salt, please? Will you help me? Could you do it for me? Would you mind opening the window?
► Commands in the reported speech
All the forms mentioned above are used in the direct speech. In the indirect speech they are is reported in a completely different way. See more at Reported commands and requests.