English Grammar - Auxillary Verbs

Auxiliary verbs "help" other verbs show tense, mood, or voice.

In the section Verb Tenses and Forms, you can see how auxiliary or helping verbs determine the tense of verb forms and how the verb, as a whole, reveals the time or relative time of the action. Auxiliary verbs also work with verbs to show mood (indicative, imperative, or subjunctive) and to show voice (active or passive).

The Auxiliary Verb "DO"

You have already seen some of the work that "to be" and "to have" auxiliary verbs can do. Another auxiliary verb is the verb "do"; this auxiliary "helps" the writer form questions or interrogatives, establish negative verbs, and create emphasis.

Examples:

    I did complete the assignment on time.  (Emphatic)
    Do you want to come to the theatre?   (Interrogative)
    She does not understand the question.  (Negative)

Modal Auxiliaries

We also include among the kinds of auxiliary verbs, those auxiliary verbs which we call modal auxiliaries. These helping verbs come before the main verb and express probability, obligation, ability, or necessity.

Nine modal auxiliaries or "modals" are available: must, might, may, shall, should, can, could, will, and would.

Examples:

    She should forgive his rude behaviour.  (Obligation)
    They may be in trouble for saying such things.  (Probability)
    Alexander can clean up after the guests.  (Ability)
    We must not leave the cake out in the rain.  (Necessity)

Sometimes, the modals might, would, should, and could function as past tenses for may, will, shall, and can, respectively. This function is not, however, exclusive. When we write, and need to determine a modal auxiliary verb, context is extremely important. The difference between saying to someone that they may pick the flowers and that they can pick the flowers is a critical difference in meaning. May tells them that picking the flowers is a possibility; can tells them they have the physical ability to pick the flowers.