What each auxiliary does
The auxiliary carries the tense and agrees with the subject, so the main verb after it doesn't change for he, she or it.
| Auxiliary | Job | Example |
|---|---|---|
| be | Continuous tenses | They are waiting outside. |
| be | Passive voice | The results were announced. |
| have | Perfect tenses | I have lived here since 2020. |
| do | Questions in the simple tenses | Did you see the news? |
| do | Negatives in the simple tenses | She doesn't eat meat. |
| do | Emphasis | I do understand your point. |
| Modals | Ability, possibility, advice, obligation | You must sign here. |
Auxiliary verb or main verb?
Be, have and do can also be main verbs. Ask whether there is another verb doing the main work.
"I have two sisters": have is the main verb. "I have met your sisters": have is the auxiliary and met is the main verb.
"She did her homework": did is the main verb. "Did she finish?": did is the auxiliary. A sentence can use do twice: "Did you do the reading?"
Rules for using auxiliaries
Only the first auxiliary changes for tense and person. "He has been working", not "He has being working".
Do takes the base form after it. "Does she like tea?", not "Does she likes tea?"
Not goes after the first auxiliary. "They have not arrived." In speech, contract it: haven't, isn't, doesn't, didn't.
Short answers repeat the auxiliary. "Are you ready?" "Yes, I am." "Did they call?" "No, they didn't."
Common mistakes
Wrong: Does she likes spicy food?
Right: Does she like spicy food?
Does already shows the -s, so the main verb stays in the base form.
Wrong: He don't know the address.
Right: He doesn't know the address.
With he, she and it, the present simple negative uses doesn't.
Wrong: I am agree with this view.
Right: I agree with this view.
Agree is a full verb. It needs no be in the present simple.
Wrong: Where you are going?
Right: Where are you going?
In a question, the auxiliary comes before the subject.
Using this in IELTS and PTE
Auxiliary errors are easy for an examiner or a scoring engine to notice, and they repeat across a whole essay. In IELTS Writing Task 2 and PTE Write Essay, check "I agree" (not "I am agree") and doesn't with singular subjects. In IELTS Speaking, short answers with auxiliaries ("Yes, I do, actually") sound natural before you expand your answer.
5 questions
Exercise
Try each one, then open it to check your answer.
1. Which word is the auxiliary? "The bridge was built in 1990."
was
Was helps built form the passive.
2. Complete this: "___ your parents live in Delhi?"
Do
A present simple question with a plural subject uses do.
3. Is have an auxiliary in "We have a meeting at ten"?
No, it is the main verb.
There is no other verb, so have carries the meaning.
4. Make this negative: "She has finished her essay."
She has not finished her essay.
Not goes after the first auxiliary.
5. Give a short answer: "Were you at home?" (yes)
Yes, I was.
A short answer repeats the auxiliary from the question.
Frequently asked questions
What are the three primary auxiliary verbs?+
Be, have and do. Be forms continuous tenses and the passive, have forms perfect tenses, and do forms questions, negatives and emphasis in the simple tenses.
Are modal verbs auxiliary verbs?+
Yes. Modals such as can, will, should and must are usually called modal auxiliaries. Unlike be, have and do, they never act as main verbs and never change form.
Can a sentence have more than one auxiliary?+
Yes. "The work will have been done by Friday" has three: will, have and been. The first one carries the tense and goes before the subject in a question.
Keep going
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