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Auxiliary verbs: the definition and usage of auxiliary verbs
Auxiliary verbs are important elements of English grammar. However, when we mention them, we tend to think of words like "do", "does" and "did" right? Yet, English includes a wide range of auxiliary verbs beyond these commonly known ones. Join us at PREP to dive into this grammar knowledge together!
I. What are auxiliary verbs?
Auxiliary verbs in English are used to support the main verb in a sentence. The purpose of these words is to help determine the tense, person, number, negation, and form of the main verb.
Below are some auxiliary verb examples:
- “Be” (am, is, are, was, were). For example: She is studying for her exams. ➡ The auxiliary verb “is” supports the main verb “studying” in the present continuous tense.
- “Do” (do, does, did). For example: Did you go to the party last night? ➡ The auxiliary verb “did” is used to create questions.
- “Have” (have, has, had). For example They haven’t finished their work yet. ➡ The auxiliary verb “have” negates the main verb “finished” in the present perfect tense.
- Modal verbs (can, may, must, should, would,…). For example: He can hear the music from his room sometimes. ➡ The auxiliary verb “can” supports the main verb “hear” in the sentence.
II. The indicators of auxiliary verbs in English
Below are some ways to identify and distinguish auxiliary verbs in English. Please pay close attention!
- Position in the sentence: Auxiliary verbs typically come before the main verb in a sentence, except when the sentence is a question. For example:
- She is studying for her exams. ➡ The auxiliary verb “is” comes before the main verb “studying”.
- Did you go to the party last night? ➡ The auxiliary verb “did” comes before the subject, then the main verb “go”.
- They haven’t finished their work yet. ➡The auxiliary verb "haven't" comes before the main verb "finished".
- The presence in negative and interrogative sentences:
- Auxiliary verbs are often used in negative sentences and questions to form their negative and interrogative structures. For example:
- She is not studying for her exams. ➡ The auxiliary verb “is” is used in negative sentences.
- Do you like coffee? ➡ The auxiliary verb “do” is used in questions.
- In addition, they also appear in affirmative sentences to emphasize the mentioned action. For example: I do love you.
- Common forms and tenses of auxiliary verbs: Auxiliary verbs have different forms and tenses. You can recognize the four most commonly used auxiliary verbs: "be" (am, is, are, was, were), "do" (do/does, did), "have" (have, has, had) and modal verbs (can, may, might, must, should, would, have to...).
III. The functions of auxiliary verbs in English
Auxiliary verbs in English have various functions. Below are some of the main functions of auxiliary verbs:
Function | Meaning | Example |
| Form tenses and verb forms | Form tenses and forms of the main verbs in the sentence |
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| Form negative sentences | Form negative sentences in English. |
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Form interrogative sentences
| Form questions in English |
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| Ensure the person and quantity | Determine the person, quantity and time of the main verb in the sentence. |
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| Create the passive voice | Create the passive voice in English |
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The above functions help auxiliary verbs play an important role in determining the grammar and meaning of sentences in English.
IV. The usage of auxiliary verbs in English
Two types of auxiliary verbs that are most commonly used in English are modal auxiliary verbs and lexical auxiliary verbs. Let's learn about these two common types in the auxiliary verb list below together with PREP!
1. Lexical auxiliary verbs
1.1. be
“be” (am, is, are, was, were) is used in the following cases:
Auxiliary verb | Usage | Meaning |
“be” | Indicate the current state or condition. |
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| Express the nature, characteristics, or attributes of a person or object. |
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Identify a noun or recognize a person or object.
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| Describe time. |
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| Create the passive structure |
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The auxiliary verb "be" can also be used to form different tenses and verb forms, such as the present continuous (am/is/are + V-ing), simple past (was/were + V-ed), present perfect (have/has been + V-ed), and more.
1.2. do
“do” “does”, and “did” have the following functions:
Auxiliary verb | Usage | Example |
“do/does/did” | Form negative sentences in the simple present and simple past tenses.
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| Form questions in the simple present and simple past tenses. |
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| Determine the person and quantity of the subject of the main verb in negative and interrogative sentences. Except for the auxiliary verb "did" which is used for all persons. |
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In addition, "do/does/did" stands before the main verb in sentences to emphasize the action. For example:
- I do love you.
- She did do that.
- He does like sweet candy.
1.3. have
Below is the usage of “have”. Let’s check it out with PREP!
Auxiliary verb | Usage | Example |
“have” | Form the present perfect, past perfect, and future perfect tenses.
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| Form negative or interrogative sentence structures. |
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2. Modal auxiliary verbs
The auxiliary verbs that express modality or can also be called modal auxiliary verbs commonly used in English are: can, could, may, might, must, ought to, had better, will, would, shall, and should. These modal auxiliary verbs are often used to express possibility, permission, obligation, or suggestion. Let's explore their usage together through some example sentences with PREP!
2.1. Can
“Can” has the negative form “cannot (can't)” and the past form “could”. Below are some examples of how the modal auxiliary verb “Can” is used:
Usage | Example |
Express the ability to do something | I can swim. |
Express permission, asking someone for permission to do something | Can I borrow your pen? |
Express a request or suggestion | Can you help me, please? |
2.2. Could
“Could” has the negative form “Could not (Couldn’t)”. “Could” functions both as the past form of “Can” as well as a modal auxiliary verb expressing possibility. Below are some examples of how the modal auxiliary verb “Could” is used:
Usage | Example |
Express the ability in the past | When I was younger, I could run very fast. |
Express a polite request or permission. | Could you please pass me the salt? |
Express a hypothetical action or possibility in the future. | I could go to the party tomorrow if I finish my work. |
2.3. May/Might
May/ Might have the negative form May not/ Might not, roughly translating to possibly or perhaps. What are some ways the modal auxiliary verbs May/ Might are used? Let's explore together!
Usage | Example |
| Express something that could be real or possible in the present or future. |
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| 'May/Might + be + V-ing' is used to express something that could potentially be happening in the present or future. |
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| Express permission requests, but 'may not' is used to deny a request or indicate prohibition. |
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2.4. Must
“Must” has the negative form must not (mustn't). Below are some examples of using this modal verb:
Usage | Example |
| Express something as necessary or obligatory to do in the present or future. |
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| Offering stressed or emphasized advice or requests. |
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| Putting forward a logical, certain conclusion. |
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| Must not is used to prohibit something, something that should not be done, or to warn someone not to do something |
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2.5. Have to
“Have to” is used to express something as necessary or obligatory. Let's take a look at how Have to is used through the chart below!
Usage | Example |
| Used similarly to “Must” to express notions of necessity or obligation. |
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| Used interchangeably with Must in the future tense, present continuous tense, past tense, and present perfect tense. |
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| 'do' is used with 'have to' in negative and interrogative sentences. |
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2.6. Will
Will has the negative form will not (won't), and the past form is Would. Below are some examples of using this modal verb:
Usage | Example |
| Express or predict future events and situations |
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| Predict present habitual actions |
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| Make an immediate decision being discussed |
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| Indicate willingness or determination to do something |
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| Express a promise to do something |
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| Express threats or warnings |
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2.7 Would
Would has the negative form Would not (wouldn't). Would is both the past tense of will as well as a modal verb. Below are some examples of how Would is used:
Usage | Example |
| Express past hypothetical scenarios or predictions |
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| Describe past habitual actions |
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| Make polite requests or offers (with more formality than "will") |
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| Use "Would S like/love/prefer... + to V" to politely express wants or wishes |
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| "Would you like to V?" as a way to make an invitation or offer |
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| "Would you....please?" makes a polite request. |
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| "Would you mind + verb-ing?" makes a polite, considerate request of someone. |
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| "Would rather + verb" or "Would prefer + to verb" expressions for indicating preference between options. |
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2.8. Shall
Shall is only used in the first person, with the negative form being Shall not (Shan’t). Below are some examples of how Shall is used:
Usage | Example |
| Express or predict future events/situations |
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| Ask for advice, opinions, or suggestions |
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| Use "Shall I...?" when making a suggestion |
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| Use "Shall we...?" when proposing an idea or plan |
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2.9. Should
Should has the negative form Should not (shouldn’t), loosely translated as expressing what is best or recommended to do. Below are some examples of using Should:
Usage | Example |
| Express obligation or necessity, though less strong than Must or Have to. | You should eat more fruits and vegetables for a healthier diet. |
| Ask for advice, opinions, or suggestions in a question form. | Should I call the doctor for an appointment? |
V. Special cases
Below are some words that function as both regular verbs and modal auxiliary verbs depending on context:
Special case | Usage | Example |
Need | Need V: Considered a modal verb denoting necessity. | You needn’t clean that car |
Dare | Dare V: Also considered a modal verb, though the construction "Dare + bare infinitive" is less common. | Dare you tell him? |
Used to | Used to V: Describes habitual past actions. | I used to play the piano when I was younger. |
Used S to V?: Also functions as a modal verb in questions. | Did you use to go there? | |
Ought to | Ought to V: Suggests or recommends an action, similar to "should.” | You ought to apologize for what you said. |
(-): Ought not to V (Oughtn’t) to V | You ought not to smoke in public places. | |
(?): Ought S to V? | Ought I to call her and check on her? |
VI. Exercises on auxiliary verbs with detailed answers
Exercise 1: Complete the following sentences with the appropriate form of “can” or “could”.
- She _____ speak five languages fluently.
- _____ you please open the window?
- When I was younger, I _____ run for hours without getting tired.
- _____ you lend me your pen, please?
- I’m not sure if I _____ attend the meeting tomorrow.
Exercise 2: Fill “can”, “could” or “might” in the appropriate blanks
- It _____ rain later, so we should bring umbrellas.
- _____ you please pass me the salt?
- I’m not sure if I _____ make it to the party tonight.
- When I was younger, I _____ climb trees.
- _____ I use your phone to make a call?
Exercise 3: Complete the following sentences with the appropriate form of “do, does, did”.
- She _____ her homework every day.
- _____ they play soccer on weekends?
- He _____ his breakfast this morning.
- _____ you like to dance?
- We _____ a great time at the party last night.
Answer keys:
Exercise 1 | Exercise 2 | Exercise 3 |
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Hopefully, the article about auxiliary verbs provided by PREP above has helped you understand more deeply the meaning and usage of this grammatical item. Keep looking forward to PREP's upcoming articles!
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