General overview

On this page you'll find out what an auxiliary verb is and how to use it.

Auxiliary verbs could be called helping verbs: they don't mean anything when they are alone, but when in a sentence, they help complete the form and meaning of main verbs. The most common auxiliary verbs are:

There are two verbs in each of these sentences:

Subject	auxiliary verb	main verb	rest of the sentence
I	have	lost	my keys.
She	doesn't	like	this band.
The hotel	was	built	ten years ago.

In the above examples, the verbs in bold are auxiliary verbs.

Now that you know what an auxiliary verb is, let's see how they can be used in greater detail.

Short answer

Use an auxiliary verb when you want to avoid repeating some part of your sentence (because it can be deduced from the context):

Person A: Have you locked the door? Person B: Yes, I have. (instead of "I have locked the door")
George wasn't working, but Janet was. (instead of "Janet was working")
She could lend me the money, but she won't. (instead of "she won't lend me the money")
Person A:Are you angry with me? Person B: Of course I'm not. (instead of "I'm not angry")

Use "do", "does" or "did" for the present and past simple:

Person A: Do you like onions? Person B: Yes, I do (instead of "I like onions")
Person A: Does Mark smoke? Person B: He used to, but now he doesn't any more (instead of "He used to smoke, but now he doesn't smoke any more")

Polite interest

Apart from that, phases such as "have you?", "isn't she?" or "do they?" and so on, can be used to show polite interest in what somebody has said:

Person A: I have just met Simon. Person B: Oh, have you. How is he?

Sometimes we use these "short questions" to show surprise:

Person A: Jim and Nora are getting married. Person B: Are they?

We use auxiliary verbs with "so" and "neither":

Person A: I'm feeling tired. Person A: So am . (instead of "I'm feeling tired too")
Person A: I never read newspapers. Person B: Neither do I. (instead of "I never read newspapers either")
Sue hasn't got a car and neither has Martin.

Note the word order after "so" and "neither" (verb before subject):

I passed the exam and so did Tom. (not: "so Tom did")

You can use "nor" instead of "neither":

Person A: I can't remember his name. Person B: Nor can I. Or: Neither can I.

You can also use "not... either".

Person A: I haven't got any money. Person B: Neither have I. Or: Nor have I. Or: I haven't either.

"I think so" / "I hope so"

After certain verbs you can use "so" if you don't want to repeat something:

Person A: Are those people English? Person B: I think so. (Meaning: "I think they are English")
Person A: Will you be at home tomorrow morning?Person B: I expect so. (Meaning: "I expect I'll be at home.")
Person A: Do you think Kate has been invited to the party? Person B: I suppose so. You can also say: "I hope so ", "I guess so" and "I'm afraid so" .