What Is an Auxiliary Verb? | Definition & Examples

Auxiliary verbs (also called helping verbs) are used along with a main verb to express tense, mood, or voice. For example, in the statement “it is raining,” “is” functions as an auxiliary verb indicating that the action of the main verb (“raining”) is ongoing.

Auxiliary verbs are used in various verb tenses, including the continuous tense (e.g., “I am talking”), the perfect tense (e.g., “you have run”), and the future tense (e.g., “they will dance”).

Examples: Auxiliary verbs in a sentence
Alice has been working here for a month.

Shaun was eating dinner when his friends arrived.

Do you know how to get to the theater?

How are auxiliary verbs used in sentences?

Auxiliary verbs are always used along with a main verb to indicate tense, mood, and voice. Auxiliary verbs typically come before the main verb in a sentence.

The primary auxiliary verbs are be, have, and do. Some sentences (e.g., those in the perfect continuous tenses) contain more than one auxiliary verb.

Examples: How to use auxiliary verbs
Eric is talking to Laura.

Jess has already eaten dinner.

Did you go to school yesterday?

Aria has been living in China for a year.

Modal auxiliary verbs (also called simply modal verbs) help to clarify the context of a sentence. They express possibility (e.g., “might”), ability (e.g., “can”), permission (e.g., “may”), and necessity (e.g., “must”). The modal verb “will” is used to form all future tenses.

While regular auxiliary verbs follow subject-verb agreement, modal auxiliary verbs never change form. In sentences containing modal verbs, the main verb typically takes the infinitive form (e.g., “he can sing”).

Examples: Modal auxiliary verbs
I would expect nothing less.

We should schedule an interview with the preferred candidate.

Shall we order dessert?

Check for common mistakes

Use the best grammar checker available to check for common mistakes in your text.

grammar-checker-common-mistakes

Fix mistakes for free

Auxiliary verbs and tense

Conjugated forms of the auxiliary verbs “be” and “have” are used in various verb tenses to help indicate time. In the future tense, the modal auxiliary verb “will” is also used.

Below is a table that shows the conjugated forms of the verb “read” in the first person singular. The table illustrates the use of auxiliary and modal verbs in creating the progressive, perfect, and perfect progressive aspects.

Past Present Future
Progressive I was reading. I am reading. I will be reading.
Perfect I had read. I have read. I will have read.
Perfect progressive I had been reading. I have been reading. I will have been reading.
Note
The modal verb “will” is used in all aspects of the future tense, including the future simple (e.g., “I will run”). The past simple and present simple (e.g., “I ran,” “I run”) don’t use auxiliary or modal verbs.

Auxiliary verbs and mood

The grammatical mood of a verb indicates the tone and intention of a sentence. Auxiliary verbs and modal verbs are used along with a main verb to express grammatical mood.

Grammatical mood Function Example
Indicative State a fact “Ravi is working.”
Imperative Express a command or a request (often with a negative auxiliary verb) Don’t break anything.”
Interrogative Ask a question Have you eaten yet?”
Conditional Express a condition “You can use my phone if you need to.”
Subjunctive Express a wish, doubt, or hypothetical situation “If I were more athletic, I would play basketball.”

Auxiliary verbs and the passive voice

Passive constructions (i.e., sentences in which the subject is the recipient of the action) use a conjugated form of the auxiliary verb “be” along with the past participle of the main verb. Sometimes, sentences in the passive voice also contain a prepositional phrase indicating the person or thing performing the action.

Example: Auxiliary verbs in a passive sentence
The boy was bitten by a dog.

Check for common mistakes

Use the best grammar checker available to check for common mistakes in your text.

grammar-checker-common-mistakes

Fix mistakes for free

Other uses of auxiliary verbs

Auxiliary verbs have various other functions in English. They can be used:

Question tags

Question tags are used at the end of a sentence to ask whether a preceding statement is true. If the main statement is positive, the question tag should use a negative auxiliary verb. If the main statement is negative, the question tag should use a positive auxiliary verb.

Question tags use the same auxiliary verb as the main statement. They also refer to the same subject. However, they always use subject pronouns (e.g., “I,” “he,” “she,” “we”).

Examples: Auxiliary verbs in question tags
Paula is coming to the party, isn’t she?

You don’t work on Saturdays, do you?

Note
If the main statement doesn’t contain an auxiliary verb, the question tag uses a conjugated form of the verb “do” along with the adverb “not” (e.g., “Laura comes from Germany, doesn’t she?”).

To avoid repetition

Auxiliary verbs are often used to avoid repeating the main verb in a sentence. Instead, a conjugated form of the main statement’s auxiliary verb is used along with the coordinating conjunction “but” and the relevant noun or pronoun. If the main statement is positive, the second statement should use a negative auxiliary verb, and vice versa.

Examples: Auxiliary verbs to avoid repetition
I don’t really like soccer, but Emily does. [she does like soccer]

Kim is tidying the house, but her sisters aren’t. [they aren’t tidying the house]

Note
If the main statement doesn’t contain an auxiliary verb, the second statement should use a conjugated form of the verb “do” (e.g., “Sara believed Harry’s story, but Una didn’t”).

Negative statements

Most negative statements are formed by adding the adverb “not” between the auxiliary verb and the main verb (or after the first auxiliary verb if the sentence contains more than one).

Examples: Auxiliary verbs in negative statements
I am not going to the party.

They had not been traveling long when they ran out of money.

To create a negative version of a sentence that didn’t originally contain an auxiliary verb, use a conjugated form of the auxiliary verb “do” along with “not” and the infinitive form of the main verb.

Examples: Negative statements using “do”
I didn’t lose the car keys.

Tess doesn’t like classical music.

Emphasis

In everyday conversation, people sometimes place emphasis on an auxiliary verb to refute or contradict a previous statement or question. When written down, the emphasized word is often italicized.

Examples: Auxiliary verbs emphasizing a statement
Why aren’t you studying?

I am studying!

You don’t know what you’re talking about.

I do know what I’m talking about!

Other interesting language articles

If you want to know more about commonly confused words, definitions, common mistakes, and differences between US and UK spellings, make sure to check out some of our other language articles with explanations, examples, and quizzes.

Frequently asked questions

What is a helping verb?

Helping verbs (also called auxiliary verbs) are used along with a main verb to express tense, mood, or voice.

For example, in the statement “We were running,” “were” is an auxiliary verb indicating that the action of the main verb, “running,” was taking place in the past.

Is “was” a helping verb?

“Was” (along with all conjugated forms of the verb “be”) is classed as an auxiliary verb when it’s used along with another (main) verb (e.g., “I was reading”).

However, when used without another verb, “was” is a linking verb that connects the subject of a sentence to a subject complement (e.g., “my father was a baker”).

Is it “could of” or “could have”?

“Could” is a modal verb that’s often used along with the auxiliary verb “have” to indicate that something was possible in the past but no longer is (e.g., “I could have become a pilot, but I didn’t”). It can be contracted to “could’ve.”

People sometimes mistakenly write “could of” because of its similar pronunciation. “Could of” is never correct.

Sources in this article

We strongly encourage students to use sources in their work. You can cite our article (APA Style) or take a deep dive into the articles below.

This Scribbr article

Ryan, E. (2023, December 18). What Is an Auxiliary Verb? | Definition & Examples. Scribbr. Retrieved April 9, 2024, from https://www.scribbr.com/verbs/auxiliary-verb/

Sources

Aarts, B. (2011). Oxford modern English grammar. Oxford University Press.

Butterfield, J. (Ed.). (2015). Fowler’s dictionary of modern English usage (4th ed.). Oxford University Press.

Garner, B. A. (2016). Garner’s modern English usage (4th ed.). Oxford University Press.

Is this article helpful?
Eoghan Ryan

Eoghan has a lot of experience with theses and dissertations at bachelor's, MA, and PhD level. He has taught university English courses, helping students to improve their research and writing.