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University of Illinois at Urbana-Champaign

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Grammar Handbook: Auxiliary Verbs

Auxiliary or helping verbs are verbs that are used to help form verb phrases but cannot do so independently. There are four basic auxiliary verb groups:

To Be

This auxiliary verb is used in the progressive tenses and passive voice:

Progressive Tense:

Passive Voice:

To Have

This verb is used as an auxiliary in the perfect tense:

Model Auxiliaries

These auxiliaries affect the mood of the verb; that is, they determine whether a verb is a fact, desire, possiblity, or command. They are most commonly used to represent degrees of freedom or severity.

Most common modal auxiliaries: will, shall, can, may, need (to), dare, would, should, could, might, must, ought (to)

To Do

This verb is used when the main verb of the sentence requires aid of an auxiliary, but there is no other helping verb that will fit. It is often used in questions, negative or emphatic statements: