Auxiliary Verbs

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What Are Auxiliary Verbs?

An auxiliary verb is used with a main verb to help express the main verb's tense, mood, or voice. For example (auxiliary verbs highlighted, main verbs in bold):

• Tense. The tense of a verb tells us when the action took place.
• Sally was eating the cake.
• Mood. The mood of a verb tells us how it is to be regarded (e.g., as a fact, a command, a wish).
• Do eat the cake, Sally.
• Voice. The voice of a verb tells us whether the subject is acting or being acted upon.
• The cake was eaten by Sally.

The main auxiliary verbs are "to be," "to have," and "to do." They appear in the following forms:

• to be: am, is, are, was, were, being, been, will be
• to have: has, have, had, having, will have
• to do: does, do, did, will do

There is another kind of auxiliary verb called a modal auxiliary verb (or modal verb). The modal auxiliary verbs are can, could, may, might, must, ought to, shall, should, will, and would. The modal auxiliary verbs never change their forms.

Examples of Auxiliary Verbs Expressing Tense

Here are some examples of auxiliary verbs expressing tense. In these examples, the main verbs are in bold and the auxiliary verbs are highlighted.

• She was waiting for an hour.
• She is waiting in the hall.
• She will be waiting outside.
(In each of these examples, the auxiliary verb to be helps to form the progressive tense, which is the tense used for ongoing actions.)

• She had drunk it before we arrived.
• She has drunk it already.
• She will have drunk it by then.
(In each of these examples, the auxiliary verb to have helps to form the perfect tense, which is the tense used for expressing an action's completion.)

• She had been studying before the incident.
• She has been studying.
• She will have been studying for a month at that point.
(In each of these examples, the auxiliary verbs have and been help to form the perfect progressive tense, which is the tense used for expressing an ongoing action's completion.)

Read more about the tenses.

Examples of Auxiliary Verbs Expressing Voice

Here are some examples of auxiliary verbs expressing voice.

• Our dessert was eaten by the dog.
• The geese are driven through the snicket.
• The phone will be disconnected tomorrow.
(In these examples, the auxiliary verb to be helps to form the passive voice. A verb is said to be in the passive voice when its subject does not perform the action of the verb but has the action done to it.)

Read more the voice of a verb.

Examples of Auxiliary Verbs Expressing Mood

Here are some examples of auxiliary verbs being used to express mood.

• Did you win?
(Here, the auxiliary verb to do is used to form the interrogative mood, i.e., to ask a question.)
• Don't forget your wallet.
(Here, the auxiliary verb to do (in its negative form) is used to form the imperative mood, i.e., to give an order.)

Read more about the mood of a verb.

Examples of Modal Auxiliary Verbs

Let's now look at the modal auxiliary verbs. Modal auxiliary verbs combine with other verbs to express ideas such as necessity, possibility, intention, and ability. In each example below, the verb phrase is in bold and the modal auxiliary verb is highlighted.

Modal auxiliary verbs expressing necessity:

• It is during our darkest moments that we must focus to see the light. (Greek philosopher Aristotle)
• I don't say we all ought to misbehave, but we ought to look as if we could. (Actor Orson Welles)
• A baby is God's opinion that life should go on. (American Poet Carl Sandburg)

Modal auxiliary verbs expressing possibility:

• It is never too late to be what you might have been. (George Eliot)
• If there were no bad people, there would be no good lawyers. (Author Charles Dickens)

Modal auxiliary verbs expressing intention:

• We shall heal our wounds, collect our dead and continue fighting. (Founding father of the People's Republic of China Mao Zedong)

Modal auxiliary verbs expressing ability:

• No one can feel as helpless as the owner of a sick goldfish. (Cartoonist Kin Hubbard)
• Well, either side could win it, or it could be a draw. (Football manager Ron Atkinson)
(Sometimes, more than one sense is expressed. Here, could expresses both ability and possibility.)

Be, have and do are not always auxiliary verbs. Here they are as the main verbs (in bold) being supported by auxiliary modal verbs (highlighted).

• I have inspiration. If I was educated, I would be a damn fool. (Musician Bob Marley)
(That should be were educated, Bob. Just sayin'.)
• I really like vampire books. I might have a problem. (Irish writer Sarah Rees Brennan)
• If you can dream it, you can do it. (Enzo Ferrari)

There's another related term we should cover: verb phrase. A verb phrase is made up of the main verb and any auxiliary verbs. Any adverbs that appear alongside or inside a verb phrase are not part of the verb phrase. In each example below, the verb phrase is in bold with auxiliary verbs highlighted.

• Rose has been drinking heavily since breakfast.
(The adverb heavily is not part of the verb phrase.)
• Peter is definitely taking you to the airport.
(The adverb definitely is not part of the verb phrase.)

Read more about modal verbs.

Why Auxiliary Verbs Are Important

I'd wager you use auxiliary verbs and modal auxiliary verbs without giving them a second thought, so I'm mindful that this page has covered a lot of gumpf that you don't really need. Well, that's true provided we're talking about working in English. If you start learning a foreign language, it won't be too long before you'll be unpicking how they express tense, voice and mood. And, do you know what's a good starting point for that? Understanding how we do it.

That said, there are three noteworthy points related to auxiliary verbs.

(Point 1) Don't write could of, should of, or would of.

If you ever write could of, should of, or would of, you're toast. It's a writing howler. It's could've (a contraction of could have), should've (should have), or would've (would have).

(Point 2) Use can for ability and may for permission.

Can is a modal auxiliary verb meaning to be able to. May is a modal auxiliary verb meaning to be permitted to.

• I can whistle.
(I have the ability to whistle.)
• May I have a biscuit?
(Am I permitted to have a biscuit?)

• "Can I go outside, grandma?"
• "You can, dear. You're just not allowed."

Nowadays, can is often used for permission, especially in an informal setting.

• Can I have a biscuit, grandma?
• "You can, dear. You're just not allowed one."
(Can is fine here, but, hey, it's still a grandma's job to issue a "correction.")

Read more about today's leniency with can and may.

(Point 3) Expand can't to cannot not can not.

Cannot (one word) is the most common expansion of the contraction can't.

• You cannot escape the responsibility of tomorrow by evading it today. (US President Abraham Lincoln)
• There cannot be a crisis next week. My schedule is already full. (US statesman Henry Kissinger)

Can't can also be expanded to can not (i.e., two words), but this is less common and usually reserved for emphasis.

• I cannot do it!
(Can't is usually expanded to cannot.)
• I can not do it!
(This is considered more emphatic.)

Of course, the words can and not sometimes appear alongside each other when the not forms part of another construction (such as not only).

• Kevin can not only rap but dance too.
(Here, can not must be written as two words. It's not an expansion of can't.)

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