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”).

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.

Modal auxiliary verbs

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”).

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.

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.

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.

Other uses of auxiliary verbs

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

• As question tags
• To avoid repetition
• In negative statements
• For emphasis

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”).

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.

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).

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.

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.

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.