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There are two basic classifications of auxiliary verb, Primary and Modal. There are three Primary auxiliaries and ten Modals. But before we get started, what’s an auxiliary verb?

In a sentence, we always have a main verb. For example, if we can only find one verb in a sentence, then we know it’s the main verb.

~ Sally plays the drums.

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However, sometimes we have multiple verbs that go together in a sentence; in this case, at least one must be an auxiliary verb. The Future Simple, for example, is formed like so:

~ I will eat cake later.

The main verb, “eat,” is complimented by the modal auxiliary verb “will.” The main verb communicates the action in a sentence, while the auxiliary verb gives us information about the tense, mood, and voice of the main verb. For example, they can indicate when the main action occurs (will, have), how likely it is (may, might, could) or even to what extent it’s mandatory (should, ought, must).

The Primary auxiliaries are “be,” “have,” and “do.” “Be is used for the continuous tenses and the passive voice.

~ We are learning English.
~ I’ll be working at this time tomorrow.
~ The car was fixed by the mechanic.


“Have” is used for the perfect tenses, like the Present Perfect, the Past Perfect, etc.

~ He has lived here for two years.
~ I had done it before she arrived.


We use “do” for the Present Simple and the Past Simple, normally in questions and negative sentences (one exception: the ‘emphatic do’).

~ Do you know karate?
~ I didn’t read my book last night.


Apart from the Primary auxiliaries, we also have the Modal auxiliary verbs (we can simply call them ‘modals’). There are ten modals: “can,” “could,” “shall,” “should,” “will,” “would,” “may,” “might,” “must,” and “ought.” Unlike the Primaries, we can’t conjugate the modals; they always stay the same. They generally express necessity or possibility, but we can’t necessarily classify each and every one into one of those categories.

~ Thomas can write with both hands.
~ Shall we go to the park?
~ You can’t smoke on airplanes. (necessity, negative)
~ We might have pizza for dinner. (possibility)


With modals, we use the infinitive without “to.” The only exception to this rule is “ought.”

~ You ought to get a good jacket before going to Alaska in December.

When making questions with auxiliary verbs, we simply move the auxiliary to the beginning of the sentence, and put the subject after it. Let’s look at a sentence first, then the same sentence in question form.

~ She will pass the exam. (sentence)
~ Will she pass the exam? (question)
~ I have been to New York. (sentence)
~ Have I been to New York? (question)


Now that you’ve learned something about auxiliary verbs, try the exercise below.


A. Edstrom

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