Auxiliary Verbs: Definition, Examples, List & Types

Auxiliary verbs often called helping verbs support the main verb in forming tenses, voices, and moods. The three main auxiliary verbs in English are “be,” “have,” and “do.” These are known as primary auxiliaries. Modal auxiliaries such as “can,” “may,” “must,” “shall,” “will,” and others form a second group that expresses necessity, possibility, or ability.

The verb “be” helps create continuous and passive verb forms. For instance, in “She is reading,” “is” works with “reading” to show an ongoing action. In “The report was written,” “was” indicates a passive voice. Similarly, “have” forms perfect tenses “They have finished the work” uses “have” to show a completed action with present relevance. Meanwhile, “do” assists in forming questions and negatives (“Do you like coffee?” “I do not know him.”) and can add emphasis (“I do agree”).

These verbs are indispensable in sentence construction because they clarify time, mood, and aspect. Understanding their function helps learners build grammatically accurate and natural-sounding sentences. Mastering the primary auxiliaries lays a foundation for handling more complex verb structures and communicating effectively in both spoken and written English.

Modal auxiliaries differ from primary auxiliaries in both purpose and form. While primary auxiliaries (“be,” “have,” “do”) help construct grammatical structures, modal auxiliaries such as “can,” “could,” “may,” “might,” “must,” “shall,” “should,” “will,” and “would” express a speaker’s attitude toward the action. They convey possibility, ability, permission, obligation, or prediction rather than merely forming tense or voice.

A key distinction lies in how they behave grammatically. Modal auxiliaries do not change form to show tense or agree with the subject; for example, “He can go” and “They can go” both use “can.” In contrast, primary auxiliaries change according to subject and tense (“She is,” “They are,” “He has,” “They have”). Modals are always followed by a base verb (“You should study,” not “You should studying”), making them simpler structurally but richer in meaning.

In practical use, modals help shape tone and subtlety. “You must finish this” shows necessity, while “You might finish this” suggests possibility. They are essential in professional writing, polite requests, and expressing uncertainty. Recognizing these differences empowers learners to communicate more precisely, reflecting intention, probability, or obligation rather than simple grammatical time or aspect.

Auxiliary verbs are crucial in forming passive and perfect tenses. In the passive voice, the auxiliary “be” combines with a past participle to shift focus from the doer to the action or recipient. For instance:

• “The book was written by the author.”
• “The project is being completed today.”
• “The emails have been sent already.”

These examples highlight how “be” changes form (is, was, were, been, being) to match the tense while the main verb stays in past participle form. Passive voice is widely used in formal and academic writing to emphasize results over agents.

In perfect tenses, the auxiliary “have” works with a past participle to indicate completed actions. Examples include:

• “She has finished her assignment.”
• “They had left before you arrived.”
• “We will have completed the course by next week.”

Each shows how “have” shifts meaning across time present perfect, past perfect, and future perfect by marking completion relative to another point in time. Both “be” and “have” auxiliaries enhance sentence precision by signaling when or how an action occurred, making them indispensable tools for expressing time, focus, and completion in English grammar.

The auxiliary “do” plays a unique role in English syntax. It appears when forming questions, negatives, and emphatic statements in simple present and simple past tenses. The basic rule: when there is no other auxiliary verb, “do” steps in to carry tense and subject agreement.

For questions, the structure is:
Do/Does/Did + subject + base verb.
Examples: “Do you work here?” “Does she play tennis?” “Did they attend the event?”
Note that “do” changes with tense and subject (“does” for third-person singular, “did” for past). The main verb remains in its base form regardless of tense.

For negation, “do” combines with “not”:
Subject + do/does/did + not + base verb.
Examples: “I do not know,” “She doesn’t eat meat,” “We didn’t go yesterday.”
Contracted forms like “don’t,” “doesn’t,” and “didn’t” are common in spoken English.

Finally, emphatic use emphasizes truth or contrast: “I do understand your point.”
Understanding these rules helps learners form grammatically correct sentences while avoiding redundancy (never say “don’t doesn’t” or “didn’t went”). Mastering “do” is key to fluent English question patterns and clear negation.

Practicing identification of auxiliary verbs strengthens sentence analysis and grammatical accuracy. Begin with sentence breakdown exercises. 

For example:

• Identify the auxiliary in “She is reading a book.” (“is”)
• Spot the helping verb in “They have finished their homework.” (“have”)
• Find the modal in “You should leave now.” (“should”)

Next, use transformation exercises. Convert statements into questions or negatives using appropriate auxiliaries. For instance, change “He plays cricket” to “Does he play cricket?” or “He does not play cricket.” This reinforces how auxiliaries change sentence function while maintaining meaning.

Another practice is tense reconstruction. Provide base verbs and ask learners to form sentences in continuous, perfect, or passive tenses using correct auxiliaries. Example: from “write,” form “is writing,” “has written,” “was written.”

For deeper understanding, include real-world context analyze headlines, news stories, or dialogues to underline auxiliaries. For example, highlight “will be announced” or “has been approved.”

Consistent exposure to varied examples helps learners internalize patterns, improving both grammar and fluency. Structured exercises like these enable automatic recognition of auxiliaries, making sentence construction intuitive and error-free.

An auxiliary verb is a verb used alongside a main verb to help indicate tense, mood, voice, or aspect. These verbs are often called “helping verbs” because they support the main verb in expressing a complete idea in a sentence.

There are two main types of auxiliary verbs: primary auxiliaries (be, have, do) and modal auxiliaries (can, could, may, might, must, shall, should, will, would, ought to). Primary auxiliaries help form various tenses and voices, while modal auxiliaries convey ability, possibility, permission, or obligation.

Primary auxiliaries (be, have, do) are used to form tenses, voice, and questions. Modal auxiliaries (can, could, may, might, must, shall, should, will, would, ought to) express attitudes or moods such as possibility, necessity, permission, or ability. Modal verbs do not change form and are always followed by the base verb.

Yes. Examples include:

• “She is reading a book.” (is – primary auxiliary)
• “They have completed their project.” (have – primary auxiliary)
• “You must submit your homework.” (must – modal auxiliary)
• “Can I use your pen?” (can – modal auxiliary).

The core list includes:

• Be: am, is, are, was, were, being, been
• Have: have, has, had
• Do: do, does, did
• Modal verbs: can, could, may, might, must, shall, should, will, would, ought to.

Auxiliary verbs are essential because they help form different verb tenses, create questions and negatives, construct the passive voice, and express necessity, ability, or possibility. Mastering auxiliary verbs leads to more accurate and versatile sentence construction.

Look for verbs that come before the main verb and help determine tense, mood, or voice. For example, in “She has been studying,” ‘has’ and ‘been’ are auxiliaries, and ‘studying’ is the main verb.

Typical mistakes include incorrect subject-verb agreement (“He don’t know” instead of “He doesn’t know”), using unnecessary auxiliaries (“I am knowing” instead of “I know”), or mixing verb forms with modals (“He can goes” instead of “He can go”).

Use modal auxiliary verbs when expressing ability (can), possibility (may, might), necessity or obligation (must, should), permission (may, can), advice (should, ought to), or making polite requests (would, could).

Auxiliary verbs make questions by appearing before the subject (“Did you finish?”) and create negatives by pairing with ‘not’ (“She does not agree”). Modal auxiliaries do the same (“Can you help?”; “She cannot attend”).