Auxiliary Verbs in English Grammar

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What is an auxiliary verb?

An auxiliary verb is a helping verb; it plays a supporting role in a sentence.

Generally, auxiliary verbs appear together with a main verb and are used to form compound tenses (have done, am going …), negatives (don’t like, didn’t see …), questions (do you work?) and question tags (you understand, don’t you?).

Auxiliary verbs also stand alone as part of short answers.

Read on to learn about auxiliary verbs in English, then practise using them in the exercises.

Auxiliary verbs vs. main verbs

Let’s start by clarifying the difference between a main verb and an auxiliary.

  • Main verbs carry meaning; they express the action of a sentence.
I drive a red car.
  • Auxiliary verbs have no meaning of their own; their role is strictly grammatical.
Today I am driving a blue car.
auxiliary = be; main verb = drive

The verbs be, do and have can be both main verbs and auxiliaries — sometimes even in the same sentence!

I have a car.
have = main verb (meaning own)
I have lost my car keys.
have = auxiliary; lose = main verb
I have had my car for three years.
have = auxiliary and main verb

Remember: the auxiliary verb comes first and is conjugated, while the main verb remains in the infinitive, past participle or present participle depending on the tense.

I have lost my car keys.
but: She has lost her car keys.
have becomes has in the 3rd person; lost stays the same

When to use an auxiliary verb

Now we know how to identify auxiliary verbs, let’s look at when to use them.

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Auxiliary verbs in compound tenses

Compound tenses are made up of two or more verbs: one auxiliary verb that is conjugated and one main verb that appears as an infinitive or a participle.


The verb be is the auxiliary for continuous tenses like the present progressive and past progressive.

I am driving to the coast tomorrow. (present progressive)
We were looking for the keys when the phone rang. (past progressive)


The verb have is the auxiliary for perfect tenses such as the present perfect and past perfect.

I have lost my car keys. (present perfect simple)
We had forgotten to get petrol. (past perfect simple)

have and be

The perfect continuous tenses use both have and be as their auxiliaries. Note: only have is conjugated; be remains as the past participle been. The main verb follows in the -ing form.

I have been driving for hours. (present perfect progressive)
Paula had been looking for her keys. (past perfect progressive)


Will is the auxiliary for the future tenses. It’s technically a modal auxiliary verb, but you can read more on those below.

I will drive home later. (will future)
I will be travelling this time tomorrow. (future progressive)

Learn more about compound and simple tenses in English grammar.

Negative and question auxiliaries (do)

In the simple present and simple past, we use the auxiliary verb do to form negatives and questions. It always appears with a main verb in the infinitive.

I don’t drive at night.
Do you have a car?

In the simple present 3rd person singular, do becomes does.

She doesn’t take the bus.
Does she take the train?

In the simple past, do becomes did.

Tom didn’t sell his old car.
Did he buy a new car?

Learn more about negation and interrogative forms in English grammar.

Auxiliaries for emphasis

Do (and its conjugated forms) appears as an auxiliary in affirmative statements to do the following:

  • add emphasis
The extra salt really does make a difference.
  • express surprise
To my surprise my order did arrive on time.
  • contradict a previous statement
—I bet they didn’t find the final clue.
—They did find it!
  • introduce a contrast
Paula doesn’t eat meat but she does eat fish.

Short answers

Auxiliary verbs are required to form short answers to yes/no questions.

Short answers are formed as follows: yes/no + subject + auxiliary verb

—Do you like tomatoes?
— Yes, I do. / No, I don’t. (simple present)
—Are you coming to the party?
—Yes, I am. / No, I’m not. (present progressive)
—Will she pass the test?
—Yes, she will. / No, she won’t. (will future)

We can form short answers in any tense. Read more about short answers in English grammar.

Auxiliaries with so and neither

We use auxiliaries with so and neither to express agreement with a previous statement and avoid repeating the verb.

The structure is as follows: so/neither + auxiliary + subject pronoun.

So + auxiliary agrees with an affirmative statement.

—I have homework.
So do I.
= me too

Neither + auxiliary agrees with a negative statement.

—I don’t like homework.
Neither do I.
= me neither

The tense of the auxiliary reflects the tense in the original statement.

—I didn’t do my homework.
—Neither did I.
—I haven’t done my homework.
—Neither have I.

Question tags

Question tags are a way of asking for confirmation. Instead of asking a standard question, we make a statement and add on a matching auxiliary and subject pronoun.

She hasn’t left, has she?
You’ve done your homework, haven’t you?

If the statement is affirmative, the question tag is negative and vice versa. The auxiliary always matches the tense in the introductory clause.

You aren’t leaving, are you? (present progressive)
He will come, won’t he? (will future)

Sometimes the auxiliary does not appear explicitly in the main clause, but the tense of the main verb indicates which auxiliary we need.

You like chocolate, don’t you?
simple present = auxiliary don’t
They lived together, didn’t they?
simple past = auxiliary didn’t


The negative question tag for I am is aren’t:

I am clever, aren’t I?

The positive question tag follows the regular pattern.

I am not too early, am I?

Learn more about question tags in English grammar.

Modal auxiliaries

Modal auxiliary is another name for modal verbs like will, should, can …

Unlike the standard auxiliary verbs (be, do, have), the modal auxiliaries carry their own meaning and thus alter the meaning of the main verb. They introduce elements of possibility, probability, obligation …

You eat vegetables. → fact
You should eat vegetables. → advice

Check out our guide to modal auxiliaries in English.

Suggested topics

For more information and exercises on auxiliary verbs, check out the following topics: