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What Is an Auxiliary Verb? | Examples, Definition & List

Verbs updated on  February 5, 2024 8 min read
Auxiliary verbs (aka helping verbs) are verbs used alongside the main verb to change its tense, mood, or voice.

For example, in “the book was written,” “written” is the main verb and “was” is an auxiliary verb helping to form the passive voice, indicating that the subject of the sentence is receiving the action.

Auxiliary verbs also help to form tenses, including the perfect tenses (e.g., “I have eaten already”), and the continuous tenses (e.g., “they are coming”).

Examples: Auxiliary verbs in a sentence
Does he write to you?
He has lived here for a long time.
They were laughing loudly.

How are auxiliary verbs used in sentences?  

Auxiliary verbs always appear with a main verb to change its tense, voice, or mood. The three main auxiliary verbs are “be,” “have,” and “do.”

Auxiliary verbs usually come before the main verb, though other words—such as adverbs—can come between the two. The auxiliary verbs need to be conjugated for tense and for subject-verb agreement.

Examples: How to use auxiliary verbs
Theo and Jim were still swimming in the lake when it started to rain.
Do you eat meat?
She has been waiting for hours.

“Be,” “do,” and “have” can also be used as main verbs. For example, “I am a builder,” “he did the dishes,” and “she has a sister.”

Sometimes called just modal verbs, modal auxiliary verbs provide additional context regarding the possibility of something or a person’s control over something (e.g., giving permission or stating an obligation). Modal auxiliary verbs do not need to be conjugated for tense or subject-verb agreement. The same modal verbs can have different meanings depending on the context.

Examples: Modal auxiliary verbs
You can open your present now. [permission]
I can knit, but I can’t crochet. [ability]

It may be too late to go to the party. [possibility]
May I come in? [permission]

See the auxiliary verb list below for the full list of all modal verbs and their uses.

Other modal expressions (sometimes called phrasal modals, semi-modals, or semi-auxiliaries) have characteristics of auxiliary verbs and modal verbs. They’re often based on an auxiliary verb or a normal verb and change their form accordingly.

Phrasal modals precede the main verb and tend to have similar meanings to modal verbs.

We are going to start the movie soon.
We will start the movie soon.

You are supposed to wash your hands after using the toilet.
You should wash your hands after using the toilet.

Auxiliary verbs and tense

The auxiliary verbs “be” and “have” and the modal auxiliary “will” play an important role in forming tenses. The table below shows how to form each of the tenses with an example in the first person singular. Apart from “will,” these verbs all need to be conjugated for tense and subject-verb agreement.

Past Present Future
Simple No auxiliary

“I walked”
No auxiliary

“I walk”

“I will walk”
Progressive (continuous) “Be” (“was”, “were”)

“I was walking”
“Be” (“is,” “am,” “are”)

“I am walking”
“Will” + “be”

“I will be walking”
Perfect “Have” (“had”)

“I had walked”
“Have” (“have,” “has”)

“I have walked”
“Will” + “have”

“I will have walked”
Perfect progressive (perfect continuous) “Have” (“had”) + “be” (“been”)

“I had been walking”
“Have” (“have,” “has”) + “be” (“been”)

“I have been walking”
“Will” + “have” + “be” (“been”)

“I will have been walking”

Auxiliary verbs and mood

The grammatical mood of a verb or sentence indicates the attitude or intention of the speaker.

In some languages, verbs will take different and distinct forms to indicate different moods. In English, however, the same verb form can be used for different moods, and moods are often expressed through constructions rather than a specific form of the verb. These constructions can (but don’t always) include auxiliary verbs and modal verbs.

Intention Example
Indicative Make a factual or neutral statement Jashan is working at the moment.
Ask a question (interrogative) Do you want dessert?”
State a condition (conditional) I can cook dinner if you’re busy.
Imperative Make a demand or request Don’t talk to me.
Subjunctive Express a wish, demand, suggestion, doubt, or hypothetical scenario I really do wish I could be there.”

Subjunctive meanings are often expressed by modal auxiliary verbs instead of subjunctive mood constructions:

It is essential that you listen carefully.
You must listen carefully.

Some languages have other moods, such as the potential mood to indicate the probability of something, that are only expressed through modal auxiliary verbs in English.

Auxiliary verbs and the passive voice

To form the passive voice (where the subject is receiving instead of performing the action), use the auxiliary verb “be” before the past participle of the main verb

Examples: Auxiliary verbs in a passive sentence
The Hunger Games was written by Suzanne Collins.
The Taj Mahal is visited by 7 to 8 million people every year.

Other uses of auxiliary verbs

Auxiliary verbs can also be used in the following ways:

In negative statements

To make a negative statement, place the adverb "not" after the auxiliary verb (or after the first auxiliary verb if there’s more than one) and before the main verb.

Examples: Auxiliary verbs in negative statements
I have not found the book.
I will not have been staying there long when you come to visit.

If the sentence doesn’t have an auxiliary verb, use a form of “do” and “not.” “Do” is conjugated for tense and subject-verb agreement instead of the main verb, so you will always use the main verb’s infinitive form.

Examples: Negative statements using “do”
Mikhail didn't do his homework.
I don't understand trigonometry.

If “be” is the main verb and there is no auxiliary, add “not” after “be” instead of using “do” (e.g., “I am not upset”).

For emphasis

“Do” can be used alongside the main verb to emphasize it. It’s often used to contradict someone or to stress agreement with them. It can also be used to emphasize imperatives.

Examples: Auxiliary verbs emphasizing a statement
He plays the guitar very well.
He does play the guitar very well.

I think you should accept the job.
I do think you should accept the job.

If the sentence already contains an auxiliary verb (or uses “be” as the main verb), the existing auxiliary verb (or “be”) is stressed instead of adding “do.” The stressed auxiliary verb may be italicized in writing (e.g., “I am doing the dishes”).

As question tags

We use question tags at the end of sentences to ask for confirmation about or seek agreement with a statement. If the main statement is positive, the tag should be negative, and vice versa.

The auxiliary verb in the question tag should match the auxiliary verb in the main statement. If the main statement doesn’t contain an auxiliary verb, use “do” (unless the main verb is “be,” in which case use a form of “be”).

Examples: Auxiliary verbs in question tags
It is really beautiful here, isn’t it?
She has a wonderful voice, doesn’t she?
You have been there, haven’t you?
You don't like chocolate, do you?

In place of the main verb

If the main verb is already understood because it appeared earlier in the sentence or in the previous sentence, then auxiliary verbs can be used to avoid repetition.

This is common in sentences using the coordinating conjunction “but.” In this construction, if the first statement is negative, the second should be positive, and vice versa. If an auxiliary verb is used in the main statement, use the same type of auxiliary verb in the second statement. Otherwise, use “do” (unless the main verb is “be”).

Examples: Auxiliary verbs to avoid repetition
I don't drink alcohol, but my wife sometimes does.
I was watching the movie, but my brother wasn’t.
Karl took notes in the seminar, but Harry didn’t.
I am a teacher, but my husband isn't.

Auxiliary verbs are also used in place of the main verb when answering questions.

Examples: Auxiliary verbs to avoid repetition when answering questions
Q: Do you like the shirt I bought you?
A: I do.

Q: Have you been learning Spanish for a long time?
A: I have.

Auxiliary verb list

This list contains all the primary auxiliary verbs along with examples and information on how they are used.

Auxiliary verb Uses Examples
Be (is, am, are, was, were, been) Continuous tenses (the past continuous, present continuous, and future continuous) I am thinking.
With “have”—perfect continuous tenses (past perfect continuous, present perfect continuous, and future perfect continuous) She has been improving.
Passive voice The paper was graded.
Do (does, did) Interrogative sentences (questions) Do you agree?
Negative sentences He didn’t write the book
Emphasis I do like it.
Have (has, had) Perfect tenses (the past perfect, present perfect, and future perfect) I have fed the goldfish.
With “be”—perfect continuous tenses (past perfect continuous, present perfect continuous, and future perfect continuous)“I had walked” You have been reading for hours.

We also have a list of modal auxiliary verbs along with their uses and examples.

Modal verb Uses Examples
Can Permission Can you go now.
Request Can you help me?
Ability (present and future) I can speak three languages.
Possibility—something we believe is usually but not always true (present and future) Algebra can be difficult to understand.
May Permission (formal) You may speak.
Possibility—possible but uncertain or unknown He may be there.
Might Permission/request (very formal) Might I know who is calling?
Possibility—possible but uncertain or unknown He might be there.
Must Obligation—a requirement or command You must bring your passport.
Possibility—strongly expected but not certain You must must be happy about your new job.
Shall Can be used in place of “will” in future tenses (usually for human subjects) I shall call you later.
Offer or suggestion Shall I make the tea?
Obligation or command You shall not pass.
Should Possibility—likely or expected without being certain We should be there soon.
Obligation—something that is preferable or expected but isn’t necessarily required or done People should eat fruit and vegetables.
Advice or suggestion You should tell him how you feel.
Will Future tenses:

  • Possibility (certain or expected to happen)
  • Intention/volition

She will graduate this year.

I will wake up early tomorrow.
Request Will you help me?
Would Request Would you help me?
Volition (past, usually negative) She wouldn’t help me.
Talking about the future in the past I thought you would say that.
Conditionals and hypothetical scenarios If I had been there, I would have laughed.
Past habits We would meet every day for lunch.
Softening an opinion or a suggestion to make it less direct or more polite I would suggest the green dress.

Do you want to know more about commas, parts of speech, email, or other language topics? Check out some of our other language articles full of examples and quizzes.




Present participle

Concrete noun


Linking verb

Common noun

Double entendre

Participial phrase

Abstract noun


Simple present tense

Proper noun


Modal verb



Frequently asked questions about auxiliary verbs

Is “was” a helping verb?

“Was,” like other forms of “be,” can either be a main verb or a helping verb (aka auxiliary verb).

As a main verb, “be” is always a stative and linking verb (e.g., “I was a doctor”). As a helping verb, it helps to form the passive voice (e.g., “the house was sold”) and continuous tenses, such as the present continuous (e.g., “I was selling my house”).

Is it “could of” or “could have”?

Although “could of” is sometimes used in colloquial speech, the correct form is “could have” or the contraction “could’ve.”

“Could” is a modal auxiliary verb and “have” can either be an auxiliary verb or a main verb. Modals and auxiliaries are used with a main verb to change its tense, mood, or voice. When “could have” modifies a main verb, it means that something may have been possible in the past but didn’t happen (e.g., “we could have stopped for coffee if we’d left earlier”).


Sophie Shores

Sophie has a BA in English Literature, an MA in Publishing, and a passion for great writing. She’s taught English overseas and has experience editing both business and academic writing.

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