The Farlex Grammar Book > English Grammar > Parts of Speech > Verbs > Auxiliary Verbs

Auxiliary Verbs

What is an auxiliary verb?

Auxiliary verbs (also called helping verbs) are verbs that add functional meaning to other “main” or “full” verbs in a clause. They are used to create different tenses or aspects, to form negatives and interrogatives, or to add emphasis to a sentence. However, they do not have semantic meaning unto themselves.

Types of Auxiliary Verbs

Here is the complete list of auxiliary verbs:

be
do
have
can
could
will
would
shall
should
must
may
might
ought to
used to
need
dare

The primary auxiliary verbs are be, do, and have, and they are the most commonly occurring auxiliaries in English. Each can also be used as a main verb in a clause, and each is able to conjugate to reflect plurality, tense, or aspect.

The verbs can, could, will, would, shall, should, must, may, and might are known as modal auxiliary verbs. These are distinguished by the fact that they are unable to conjugate into different forms, and they are only followed by a verb in its base form.

The remaining verbs—ought to, used to, need, and dare—are known as semi-modal verbs, since they do not share all the characteristics of the modal verbs above and only function as auxiliary verbs in certain ways.

Creating verb tenses

One of the most common uses of auxiliary verbs is to create the continuous and perfect continuous verb tenses (as well as the future simple tense).

Future Simple Tense

The future tense is structured as will + the main verb, or is/am/are + going to + the main verb:

“I will arrive in New York at 10 PM.”

or:

“I am going to arrive in New York at 10 PM.”

Present Continuous Tense

The present continuous tense is structured as am/is/are + the present participle of the main verb:

“I am working tomorrow.”
“She is living in New York.”
“They are trying to save some money.”

Past Continuous Tense

The past continuous tense is structured as was/were + the present participle of the main verb:

“I was cooking breakfast when she called.”
“We were talking on the phone at the time.”

Future Continuous Tense

The future continuous tense is structured as will be + the present participle of the main verb, or am/is/are + going to be + the present participle of the verb:

“I will be leaving in the morning.”

or:

“I am going to be leaving in the morning.”

Present Perfect Tense

The present perfect tense is structured as have/has + the past participle of the main verb:

“I have lived here all my life.”
“She has studied for this exam for weeks.”
“They have tried to find a solution to the problem.”

Past Perfect Tense

The past perfect tense is structured as had + the past participle of the main verb:

“I had already made my fortune when I was your age.”
“We had seen that the results were constant.”

Future Perfect Tense

The future perfect tense is usually structured as will have + the past participle of the main verb:

“I will have finished by that time.”
“She will have sung with a professional orchestra before the tour begins.”

Present Perfect Continuous Tense

The present perfect continuous tense is structured as have been + the present participle of the main verb:

“I have been trying to reach you for over an hour.”

Past Perfect Continuous Tense

The past perfect continuous tense is structured as had been + the present participle of the main verb:

“We had been working through the night.”

Future Perfect Continuous Tense

The future perfect continuous tense is structured as will have been + the present participle of the main verb, or am/is/are + going to + have been + the present participle of the verb:

“She will have been living here for most of her life.”
“I am going to have been working here for 10 years next week.”

Identifying auxiliary verbs

Auxiliary verbs can be identified by two main criteria: whether the verb is capable of inversion with the subject, and whether it can take the negating adverb not as a postdependent modifier.

(An exception to the first two rules is the linking verb be, which can both invert and take not, despite having the function of a main verb.)

Subject-auxiliary inversion

Inversion refers to the reversal of the normal position of the subject and the auxiliary verb of a clause. While it is technically possible for a main verb to invert with its subject, it is much less likely than having an auxiliary verb cause an inversion, due to the fact that subject-auxiliary inversion is commonly used to create interrogative sentences. Additionally, subject-auxiliary inversion can be used to create conditional sentences, as well as for emphasis in negative sentences when negating phrases are used.

Interrogative sentences

When a sentence is in the present simple tense or past simple tense, we use the auxiliary verb do to form it into a question word. Do is inverted with the subject, coming before it in the sentence. For example:

“John works across town.” (declarative sentence)
“Does John work across town?” (interrogative sentence)

If the verb is in a continuous tense (present, past, or future) or the future simple tense, then the auxiliary verb used to create the tense is inverted with the subject; if the verb is in a perfect continuous tense (present, past, or future), then the first of the two auxiliary verbs is inverted. For example:

Present continuous tense:

“John is working across town.” (declarative)
“Is John working across town?” (interrogative)

Past continuous tense:

“John was working across town.” (declarative)
“Was John working across town?” (interrogative)

Present perfect continuous tense:

“John has been working across town.” (declarative)
“Has John been working across town?” (interrogative)

Past perfect continuous tense:

“John had been working across town.” (declarative)
“Had John been working across town?” (interrogative)

Future simple tense:

“John will work across town.” (declarative)
“Will John work across town?” (interrogative)

or:

“John is going to work across town.” (declarative)
“Is John going to work across town?” (interrogative)

Future continuous tense:

“John will be working across town.” (declarative)
“Will John be working across town?” (interrogative)

or:

“John is going to be working across town.” (declarative)
“Is John going to be working across town?” (interrogative)

Future perfect continuous tense:

“John will have been working across town.” (declarative)
“Will John have been working across town?” (interrogative)

or:

“John is going to have been working across town.” (declarative)
“Is John going to have been working across town?” (interrogative)

Question words and modal verbs

This inversion holds true even when a question word is used, as in:

“Where will John be working across town?”
“Why had John been working across town?”
“When was John working across town?”

Modal auxiliary verbs can also be used to create questions with specific meanings, as in:

“Can you work a forklift?” (question of ability)
“May I watch television for an hour?” (question of permission)
“Must we sit through another boring play?” (question of obligation)

Inversion of be

Finally, as we mentioned earlier, be is able to invert when it functions as a linking verb (meaning it is a main verb) as well as when it functions as an auxiliary. For example:

“I am cold.”
“Are you cold?”

“They were all present.”
“Were they all present?”

Conditional sentences

Conditional sentences are most often formed using the conjunction if to create a condition clause. For example:

“If I were to move to Florida, I would be warm all year round.”
“If they had trained a little harder, they would have won.”

We can also achieve conditional clauses by using subject-auxiliary inversion, although the sentence sounds a bit more formal as a result:

“Were I to move to Florida, I would be warm all year round.”
“Had they trained a little harder, they would have won.”

Negative phrases

Negative phrases are sometimes used to provide extra emphasis in a negative sentence. Because the main verb remains affirmative, the negative phrase appears ahead of the subject and the main verb, which means that an auxiliary verb must come between it and the subject.

If the negative phrase were to come after the main verb of the sentence (as adverbial phrases often do), the sentence would become unclear because the verb would shift from an affirmative position to a negative one. For example:

“Under no circumstances are you spending the night there.” (With subject-auxiliary inversion, the sentence is clear with proper emphasis on the negative phrase.)
“You are spending the night there under no circumstances.” (Without inversion, the sentence becomes unclear and/or lacks emphasis.)

“At no point did they tell us what the problem was.” (subject-auxiliary inversion)
“They told us what the problem was at no point.” (no inversion)

Forming negative sentences with not

The most common way to make a verb negative is to use the adverb not. However, main verbs usually do not take not on their own—they require an auxiliary verb to accomplish this. For example: