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21.6: Modal Auxiliaries

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    We all need to express our moods and emotions, both in writing and in our everyday life. We do this by using modal auxiliaries.

    Modal auxiliaries are a type of helping verb that are used only with a main verb to help express its mood.

    The following is the basic formula for using a modal auxiliary:

    Subject + modal auxiliary + main verb

    James may call

    There are ten main modal auxiliaries in English.

    Modal Auxiliary Use Modal Auxiliary + Main Verb
    Can Expresses an ability or possibility

    I can lift this forty-pound box. (ability)

    We can embrace green sources of energy. (possibility)
    Could Expresses an ability in the past; a present possibility; a past or future permission

    I could beat you at chess when we were kids. (past ability)

    We could bake a pie! (present possibility)

    Could we pick some flowers from the garden? (future permission)
    May Expresses uncertain future action; permission; ask a yes-no question

    I may attend the concert. (uncertain future action)

    You may begin the exam. (permission)

    May I attend the concert? (yes-no questions)
    Might Expresses uncertain future action I might attend the concert (uncertain future action—same as may)
    Shall Expresses intended future action I shall go to the opera. (intended future action)
    Should Expresses obligation; ask if an obligation exists

    I should mail my RSVP. (obligation, same as ought to)

    Should I call my mother? (asking if an obligation exists)
    Will Expresses intended future action; ask a favor; ask for information

    I will get an A in this class. (intended future action)

    Will you buy me some chocolate? (favor)

    Will you be finished soon? (information)
    Would States a preference; request a choice politely; explain an action; introduce habitual past actions

    I would like the steak, please. (preference)

    Would you like to have breakfast in bed? (request a choice politely)

    I would go with you if I didn’t have to babysit tonight. (explain an action)

    He would write to me every week when we were dating. (habitual past action)
    Must Expresses obligation We must be on time for class.
    Ought to Expresses obligation I ought to mail my RSVP. (obligation, same as may)

    Pro-Tip: Modal Auxiliary

    Use the following format to form a yes-no question with a modal auxiliary:

    Modal auxiliary + subject + main verb

    Should I drive?

    Be aware of these four common errors when using modal auxiliaries:

    1. Using an infinitive instead of a base verb after a modal

    Incorrect: I can to move this heavy table.

    Correct: I can move this heavy table.

    2. Using a gerund instead of an infinitive or a base verb after a modal

    Incorrect: I could moving to the United States.

    Correct: I could move to the United States

    3. Using two modals in a row

    Incorrect: I should must renew my passport.

    Correct: I must renew my passport. Correct: I should renew my passport.

    4. Leaving out a modal

    Incorrect: I renew my passport.

    Correct: I must renew my passport.

    Modals and Present Perfect Verbs

    In the previous section, we defined present perfect verb tense as describing a continuing situation or something that has just happened.

    Remember, when a sentence contains a modal auxiliary before the verb, the helping verb is always have.

    Subject + Modal Auxiliary + have + past participle

    I could have helped

    He could have helped

    He might have helped

    Be aware of the following common errors when using modal auxiliaries in the present perfect tense:

    1. Using had instead of have

    Incorrect: Jamie would had attended the party, but he was sick.

    Correct: Jamie would have attended the party, but he was sick.

    2. Leaving out have

    Incorrect: Jamie would attended the party, but he was sick.

    Correct: Jamie would have attended the party, but he was sick.

    See this page for video tutorials on subject-verb agreement from Kahn Academy for more help.

    21.6: Modal Auxiliaries is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

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