21.6: Modal Auxiliaries
- Page ID
- 223651
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)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.