What are Auxiliary Verbs? Definition, Use, & Examples
Learn what auxiliary verbs are and how to use them correctly. Discover the types, rules, and examples of primary and modal auxiliaries to improve your English grammar.
Auxiliary verbs play an essential role in English grammar. They help you form different tenses, voices, and moods. Without them, sentences would sound incomplete or unclear. Understanding auxiliary verbs helps you communicate more accurately and naturally.
What is an Auxiliary Verb?
An auxiliary verb is a helping verb. It works with a main verb to express tense, mood, voice, or emphasis. You use auxiliary verbs to create questions, negatives, compound verb forms, and to show different aspects of time (past, present, future).
For example:
- She is reading a book.
- They have finished dinner.
- He does not like coffee.
In each sentence, the auxiliary verb helps the main verb by adding grammatical meaning.
Why Auxiliary Verbs Matter
Auxiliary verbs make your sentences flexible and precise. They help you:
- Show time or tense (past, present, future)
- Form questions and negatives
- Add emphasis
- Create passive voice
- Express possibility, necessity, or permission
Without auxiliaries, expressing these ideas would be difficult.
Types of Auxiliary Verbs
There are two main types of auxiliary verbs:
- Primary auxiliary verbs (be, have, do)
- Modal auxiliary verbs (can, could, may, might, shall, should, will, would, must, ought to, dare, need, used to)
Primary auxiliaries form tenses and questions, while modal auxiliaries express ability, possibility, or necessity.
Let’s look at each type in detail.
Primary Auxiliary Verbs
Primary auxiliary verbs help form different tenses and structures. They can also work as main verbs. The three primary auxiliaries are be, have, and do.
1. The Auxiliary Verb “Be”
You use “be” to form continuous (progressive) tenses and the passive voice.
Forms of “be”: am, is, are, was, were, being, been.
Examples:
- I am writing an email. (Present continuous)
- They were studying all night. (Past continuous)
- The report is being reviewed. (Present continuous passive)
- The house was built in 1920. (Past passive)
The verb “be” changes form depending on the subject and tense.
2. The Auxiliary Verb “Have”
You use “have” to form perfect tenses. It shows completed actions or experiences.
Forms of “have”: have, has, had, having.
Examples:
- I have eaten breakfast. (Present perfect)
- She had finished her work before lunch. (Past perfect)
- They will have left by noon. (Future perfect)
“Have” can also appear as a main verb, meaning “to possess.”
Example:
- I have a new car. (Main verb)
3. The Auxiliary Verb “Do”
You use “do” to form questions, negatives, and emphatic sentences.
Forms of “do”: do, does, did.
Examples:
- Do you like pizza? (Question)
- He doesn’t watch TV. (Negative)
- I did finish the task! (Emphasis)
“Do” can also be a main verb meaning “to perform” or “to carry out.”
Example:
- I do my homework every day. (Main verb)
Summary Table: Primary Auxiliary Verbs
| Auxiliary Verb | Forms | Common Uses | Example Sentence |
|---|---|---|---|
| Be | am, is, are, was, were, being, been | Continuous tenses, passive voice | She is reading a novel. |
| Have | have, has, had, having | Perfect tenses | They have finished lunch. |
| Do | do, does, did | Questions, negatives, emphasis | Do you play the guitar? |
Modal Auxiliary Verbs
Modal auxiliary verbs, otherwise known as modal verbs, express ability, permission, possibility, necessity, or obligation. They always come before the main verb and never change form (except “have to” and “used to”).
Here’s a breakdown of modal auxiliaries and how you use them.
1. Can
You use can to show ability or permission.
Examples:
- I can swim very well. (Ability)
- You can leave now. (Permission)
2. Could
You use could for past ability, polite requests, or possibilities.
Examples:
- She could dance beautifully when she was young. (Past ability)
- Could you help me? (Polite request)
- It could rain later. (Possibility)
3. May
You use may to express permission or possibility.
Examples:
- You may go now. (Permission)
- It may snow tonight. (Possibility)
4. Might
You use might for weaker possibilities or hypothetical situations.
Examples:
- We might visit Paris this summer. (Possibility)
- If I studied harder, I might pass the test. (Hypothesis)
5. Shall
You use shall to express future actions or formal suggestions. It’s common in British English.
Examples:
- I shall return soon. (Future action)
- Shall we begin the meeting? (Suggestion)
6. Should
You use should for advice, expectations, or mild obligations.
Examples:
- You should eat more vegetables. (Advice)
- The train should arrive soon. (Expectation)
- Students should submit assignments on time. (Obligation)
7. Will
You use will to express the future, promises, or decisions made at the moment of speaking.
Examples:
- I will call you tomorrow. (Future)
- She will help you. (Promise)
8. Would
You use would for polite requests, hypothetical situations, or past habits.
Examples:
- Would you like some tea? (Polite offer)
- I would travel more if I had time. (Hypothesis)
- When we were kids, we would play outside every day. (Past habit)
9. Must
You use must for strong obligations, necessities, or logical conclusions.
Examples:
- You must wear a helmet. (Obligation)
- She must be tired after that long trip. (Logical conclusion)
10. Ought to
You use ought to for moral duties or advice.
Examples:
- You ought to respect your parents. (Moral duty)
- He ought to study harder. (Advice)
11. Need
You use need to express necessity. It can act as a modal or a main verb.
Examples:
- You need not worry. (Modal)
- I need a break. (Main verb)
12. Dare
You use dare to express courage or challenge. It can be a modal or main verb.
Examples:
- I dare not speak. (Modal)
- He dared to ask her out. (Main verb)
13. Used to
You use used to to talk about past habits or situations that no longer exist.
Examples:
- I used to live in London.
- She used to play the piano.
Summary Table: Modal Auxiliary Verbs
| Modal Verb | Function | Example Sentence |
|---|---|---|
| Can | Ability, permission | I can drive. |
| Could | Past ability, polite request, possibility | She could sing well. |
| May | Permission, possibility | It may rain. |
| Might | Weak possibility | We might win. |
| Shall | Future, suggestion | Shall we dance? |
| Should | Advice, obligation | You should study. |
| Will | Future, promise | I will help you. |
| Would | Politeness, hypothesis | Would you join us? |
| Must | Obligation, conclusion | You must stop. |
| Ought to | Moral duty, advice | You ought to rest. |
| Need | Necessity | You need not worry. |
| Dare | Challenge, courage | I dare not go. |
| Used to | Past habit | I used to jog daily. |
How Auxiliary Verbs Work in Sentences
Auxiliary verbs usually come before the main verb. They form verb phrases that express tense, mood, or voice.
Examples:
- She is writing a letter. (Present continuous)
- They have finished dinner. (Present perfect)
- He was invited to the event. (Passive voice)
- You must study hard. (Obligation)
If there are multiple auxiliaries, they appear before the main verb in a specific order.
Example:
- She might have been sleeping.
Here, might (modal) + have (perfect) + been (continuous) + sleeping (main verb).
After understanding how auxiliary verbs work in sentences, it’s important to know when to use them. You use auxiliary verbs to form different tenses and express actions across time. They help you describe whether something is happening now, happened earlier, or will happen later. By learning how auxiliaries function in each tense, you can make your English sound more natural and accurate.
When Do You Use Primary Auxiliary Verbs?
You use primary auxiliary verbs to form different verb tenses and express time accurately. Each tense shows when an action happens (past, present, or future) and whether it’s complete or ongoing. By using primary auxiliary verbs, you can describe time clearly and naturally.
Below are the main tenses that require primary auxiliary verbs and how they work.
Present Tenses (be, do, have)
You use auxiliary verbs in the present tense to describe actions happening now, repeated habits, or ongoing situations. The auxiliary verbs be, do, and have each serve a different purpose in present-tense forms.
- Be helps form the present continuous tense to show actions happening right now.
- Example: I am studying English.
- Example: She is working from home.
- Do helps you form negatives and questions in the simple present tense.
- Example: I do not like coffee.
- Example: Do you play tennis?
- Have helps form the present perfect tense, showing actions that started in the past and continue to the present.
- Example: They have lived here for years.
- Example: He has finished his homework.
The present tenses use these auxiliaries to express actions that are real, current, or connected to the present moment.
Past Tenses (was/were, did, had)
You use auxiliary verbs in the past tense to describe actions that already happened or were ongoing in the past. The auxiliaries be, do, and have help you form different past tenses.
- Be forms the past continuous tense to show an action that was in progress at a specific time.
- Example: I was reading when you called.
- Example: They were watching a movie last night.
- Did helps form negatives and questions in the simple past tense.
- Example: I did not go to the party.
- Example: Did you enjoy the concert?
- Had forms the past perfect tense to show an action that happened before another past action.
- Example: She had finished dinner before the guests arrived.
- Example: They had left when we got there.
You use past tenses to describe completed events, past habits, or conditions that no longer exist.
Future Tenses (will)
You use will to describe actions that have not happened yet but will occur in the future. Unlike other tenses, the future tense does not follow normal subject-verb agreement. You simply add the modal auxiliary verb will before the base form of the main verb.
Examples:
- She will start a new job next month.
- They will arrive soon.
- I will help you with your homework.
Continuous Tenses (be)
You use be to form the continuous tenses (also called progressive tenses). These tenses show ongoing actions — something that is, was, or will be in progress.
To form a continuous tense, use a conjugated form of be followed by the present participle (-ing) form of the main verb.
Examples:
- I am studying for my exams. (Present continuous)
- She was reading when I called. (Past continuous)
- They will be traveling tomorrow. (Future continuous)
Continuous tenses help you describe actions that are happening over time, not just at a single moment.
Perfect Tenses (have)
You use have to form the perfect tenses, which show actions that are completed or have lasting effects.
To build these tenses, use a conjugated form of have followed by the past participle of the main verb.
Examples:
- They have finished their homework. (Present perfect)
- I had eaten before you arrived. (Past perfect)
- By next week, she will have graduated. (Future perfect)
Perfect tenses help you show that one action happened before or affects another action in time.
Perfect Continuous Tenses (have + been)
You use both have and be to form the perfect continuous tenses. These tenses combine the ideas of completion and duration. They describe actions that started in the past and continue up to a specific time.
To form them, use a conjugated form of have, the past participle of be (been), and the present participle (-ing) of the main verb.
Examples:
- I have been working all day. (Present perfect continuous)
- He had been studying before the power went out. (Past perfect continuous)
- By next month, we will have been living here for a year. (Future perfect continuous)
Perfect continuous tenses help you show ongoing actions with a sense of time and progress.
Summary Table: Auxiliary Verbs in Tenses
| Tense Type | Auxiliary Verb(s) | Structure | Example Sentence |
|---|---|---|---|
| Present | be, do, have | am/is/are + verb-ing; do/does + base verb; have/has + past participle | I am reading. / Do you play? / I have finished. |
| Past | was/were, did, had | was/were + verb-ing; did + base verb; had + past participle | I was reading. / Did you go? / I had eaten. |
| Future | will | will + base verb | She will visit soon. |
| Continuous | be | am/is/are/was/were + verb-ing | They are waiting for you. |
| Perfect | have | have/has/had + past participle | We have finished dinner. |
| Perfect Continuous | have + be | have/has/had + been + verb-ing | He has been running since morning. |
Auxiliary verbs make it possible to express time clearly in English. You use them to show whether an action is happening now, has already happened, or will happen later. They also help you explain how long something continues or whether it’s complete.
By mastering these structures, you’ll sound more fluent and precise in both writing and speech.
Modal Auxiliary Verbs and Time
So far, you’ve seen how primary auxiliary verbs (be, have, do) help form tenses and show time. Modal auxiliary verbs also express time, but they add meaning such as ability, permission, or obligation.
Modals always appear before the main verb, and they don’t take -s endings or change form to show tense. Instead, you use context or time expressions to indicate when the action happens.
Examples:
- She can swim well. (Present ability)
- I could run faster when I was younger. (Past ability)
- You must finish this today. (Necessity)
- We will call you later. (Future intention)
Modals often show the attitude of the speaker; how certain, polite, or committed you are about the action.
Examples:
- It might rain later. (Possibility)
- You should see a doctor. (Advice)
Together, primary and modal auxiliaries give you the full range of ways to express time, mood, and meaning in English.
You can learn more about modal verbs here.
Other Uses for Auxiliary Verbs
Auxiliary verbs do more than form tenses. You also use them to build questions, create negative sentences, add emphasis, and form the passive voice. These functions are just as important for clear and natural English. Let’s look at how they work.
Using Auxiliary Verbs to Form Questions
You often use auxiliaries to form questions by placing them before the subject.
Examples:
- Do you like music?
- Have you finished your homework?
- Is she coming tonight?
- Will they join us?
Modal verbs also form direct questions.
Example:
- Can I borrow your pen?
Using Auxiliary Verbs to Form Negatives
To make negatives, add “not” after the auxiliary verb.
Examples:
- She is not coming.
- They have not finished yet.
- He does not like sushi.
- You should not worry.
You can also contract them:
- isn’t, haven’t, don’t, shouldn’t.
Auxiliary Verbs in Emphatic Sentences
You can use “do,” “does,” or “did” to add emphasis.
Examples:
- I do understand your concern.
- She does want to join.
- He did apologize sincerely.
These sentences sound more forceful and clear.
Auxiliary Verbs in the Passive Voice
You use the verb “be” as an auxiliary to form the passive voice. The main verb changes to its past participle form, and the subject receives the action instead of doing it. This shifts focus from who did the action to what happened.
Examples:
- The cake was baked by my mom.
- The letter is being written.
- The project has been completed.
It helps to understand the difference between the active voice and the passive voice.
In the active voice, the subject does the action.
Example: The chef baked the cake.
In the passive voice, the subject receives the action.
Example: The cake was baked by the chef.
Auxiliary Verbs vs Main Verbs
Auxiliary verbs assist the main verb, while main verbs show the primary action.
Examples:
- She is reading a book. (Auxiliary + main verb)
- She reads every day. (Main verb only)
Some words can serve both roles.
Example:
- I am tired. (Main verb)
- I am studying now. (Auxiliary verb)
Common Mistakes with Auxiliary Verbs
Even advanced learners make errors with auxiliaries. Here are common mistakes and how to fix them.
1. Forgetting the Auxiliary in Questions
Incorrect: You like coffee?
Correct: Do you like coffee?
2. Using the Wrong Form
Incorrect: She have gone to school.
Correct: She has gone to school.
3. Double Auxiliaries
Incorrect: She didn’t went to work.
Correct: She didn’t go to work.
4. Misplacing “Not”
Incorrect: He goes not often.
Correct: He does not go often.
5. Confusing Modal Meanings
Incorrect: You must go if you want to. (Wrong use of necessity)
Correct: You can go if you want to. (Permission)
Tips for Using Auxiliary Verbs Correctly
- Identify the main verb first.
The auxiliary supports it, not replaces it. - Use the right auxiliary for the tense.
For example, be for continuous, have for perfect. - Avoid unnecessary auxiliaries.
Don’t say “did went” or “was eaten by.” - Remember contractions.
They make speech natural (isn’t, can’t, don’t). - Pay attention to word order.
In questions, the auxiliary comes before the subject. - Learn modal meanings.
“Must” shows obligation, while “might” shows possibility.
Conclusion
Auxiliary verbs are the backbone of English grammar. They help you express time, mood, voice, and more. The three primary auxiliaries of be, have, and do combine with main verbs to form complex tenses and structures. The modal auxiliaries can, could, may, might, shall, should, will, would, must, ought to, need, dare, and used to, add meaning, possibility, and tone.
When you use auxiliary verbs correctly, your English sounds natural and precise. Just remember, always pay attention to their order, placement, and meaning.
