The Writing Center @ KUMC Modals

The Writing Center @ KUMC

Dykes Library G011 • www.kumc.edu/writing • 945-8477

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Modals

Modal verbs are helping verbs that precede another verb and add meaning to this

main verb by expressing possibility, ability, permission, or obligation. With a

modal verb, the root form of the main verb is generally used, not the infinitive

form that contains the word “to.” An exception to this is the phrase “ought to,”

which is considered a modal verb. Modal verbs are also different from other verbs

in that they never change their form. That is, they never end in “s,” “ed,” or “ing.”

Modals of Possibility

Modals can suggest the logical probability of something happening and indicate

the strength of that likelihood. The strongest modal in this case, must, is so

potent that it is almost forcing something to happen. At the other end of the

spectrum are can, could, and might, which express a faint possibility of something

occurring. These are the modal verbs for expressing present and future possibility,

from strongest to weakest:

Strongest

Must/must not, Will/won’t, Would/

wouldn’t

Stronger

Should/shouldn’t

Weaker

May/may not

Weakest

Can/can’t, Could/couldn’t,

Might/might not

Examples: David keeps yawning. He must be tired.

We will meet at the coffeehouse tomorrow at 2.

I might get a raise soon.

To express past probability, have and the past participle are added to the

following modal verbs:

 Must/must not

 Can’t

 Could/couldn’t

 Might/might not

Examples: He must have left work already.

Fido can’t have escaped through that gap in the fence—it’s too small.

Modals of Ability

These modals indicate skill or general abilities, the ability to do something at a

specific time in the present or future, or in the past. The following are modals of

ability:

 Can/can’t (present or future)

 Could/couldn’t (past)

Examples: Sarah can speak Mandarin fluently.

John could swim before he could walk.

Modals of Permission

Modal verbs of permission are used to grant approval of an action or to ask for

approval. Can and may are basically the same, but may is more formal and used

less often than can. These are the modal verbs of permission:

 Can/can’t (present or future)

 Could/couldn’t (past)

 May

Examples: You can borrow my DVD.

Yes, you may have another cookie.

Modals of Obligation

These modal verbs are used to express something that is a requirement or

necessity, or something that is a recommendation or moral obligation. The

following are the modal verbs of obligation:

 Must/must not

 Should/shouldn’t

 Ought to

Must indicates a requirement or necessity, while should and ought to is used

when giving advice or commenting on the desirability of an action.

Examples: You must be 18 years old to vote in the U.S.

You should get more sleep.

As academic writing is based on research, remember that whichever modal verb

you choose should match the level of certainty of your evidence. When writing

about research or phenomena, the simple past and simple present is appropriate.

It is when writing about theoretical topics, however, that use of modal verbs is

warranted.