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Modal Verbs

Some helping verbs, called modal auxiliaries or modals, such as can, could, may, might, must, ought to, shall, should, will, and would, do not change form for different subjects. For instance, try substituting any of these modal auxiliaries for can with any of the subjects listed below.




Some helping verbs, called modal auxiliaries or modals, such as can, could, may, might, must, ought to, shall, should, will, and would, do not change form for different subjects. For instance, try substituting any of these modal auxiliaries for can with any of the subjects listed below.


(singular)  He can write well.


We, you ,They                           (plural)


There is also a separate section on the Modal Auxiliaries, which divides these verbs into their various meanings of necessity, advice, ability, expectation, permission, possibility, etc., and provides sample sentences in various tenses. See the section on Conditional Verb Forms for help with the modal auxiliary would. The shades of meaning among modal auxiliaries are multifarious and complex.


Uses of Can and Could


The modal auxiliary can is used


         to express ability (in the sense of being able to do something or knowing how to do something):


He can speak Spanish but he can't write it very well.


         to expression permission (in the sense of being allowed or permitted to do something): Can I talk to my friends in the library waiting room? (Note that can is less formal than may. Also, some writers will object to the use of can in this context.)


         to express theoretical possibility:


American automobile makers can make better cars if they think there's a profit in it.


your text or situation. As Theodore Bernstein puts it in The Careful Writer, "a writer who is attentive to the proprieties will preserve the traditional distinction: can for ability or power to do something, may for permission to do it.


The question is at what level can you safely ignore the "proprieties." Merriam-Webster's Dictionary, tenth edition, says the battle is over and can can be used in virtually any situation to express or ask for permission. Most authorities, however, recommend a stricter adherence to the distinction, at least in formal situations.



Uses of May and Might


Two of the more troublesome modal auxiliaries are may and might. When used in the context of granting or seeking permission, might is the past tense of may. Might is considerably more tentative than may.


       May I leave class early?


       If I've finished all my work and I'm really quiet, might I leave early?


In the context of expressing possibility, may and might are interchangeable present and future forms and might + have + past participle is the past form:


       She might be my advisor next semester.


       She may be my advisor next semester.


       She might have advised me not to take biology.


Avoid confusing the sense of possibility in may with the implication of might, that a hypothetical situation has not in fact occurred. For instance, let's say there's been a helicopter crash at the airport. In his initial report, before all the facts are gathered, a newscaster could say that the pilot "may have been injured." After we discover that the pilot is in fact all right, the newscaster can now say that the pilot "might have been injured" because it is a hypothetical situation that has not occurred. Another example: a body had been identified after much work by a detective. It was reported that "without this painstaking work, the body may have remained unidentified." Since the body was, in fact, identified, might is clearly called for.



Uses of Will and Would



In certain contexts, will and would are virtually interchangeable, but there are differences. Notice that the contracted form 'll is very frequently used for will.


Will can be used to express willingness:


      I'll wash the dishes if you dry.


      We're going to the movies. Will you join us?


It can also express intention (especially in the first person):


                        I'll do my exercises later on. and prediction:


      specific: The meeting will be over soon.


      timeless: Humidity will ruin my hairdo.


      habitual: The river will overflow its banks every spring.


Would can also be used to express willingness:



•                  Would you please take off your hat?


It can also express insistence (rather rare, and with a strong stress on the word "would"):


                        Now you've ruined everything. You would act that way. and characteristic activity:


      customary: After work, he would walk to his home in West Hartford.


      typical (casual): She would cause the whole family to be late, every time.


In a main clause, would can express a hypothetical meaning:


                  My cocker spaniel would weigh a ton if I let her eat what she wants. Finally,


would can express a sense of probability:


                  I hear a whistle. That would be the five o'clock train.


U se of Shall and Should


Mainly used in American English to ask questions politely (it has more usages in British English). For the future tense, will is more frequently used in American English than shall.


            Shall we dance?

            Shall I go now?

            Let’s drink, shall we?


Often used in formal settings to deliver obligation or requirement:


            You shall abide by the law.

            There shall be no trespassing on this property.

            Students shall not enter this room.


Often used in auxiliary functions to express an opinion, suggestion, preference, or idea:


            You should rest at home today.

            I should take a bus this time.

            He should be more thoughtful in the decision-making process.


Used to express that you wish something had happened but it didn’t or couldn’t


(should + have + past participle):


            You should have seen it. It was really beautiful.

            I should have completed it earlier to meet the deadline.

            We should have visited the place on the way.


Used to ask for someone’s opinion:


            What should we do now?

            Should we continue our meeting?

            Should we go this way?

            Where should we go this summer?


Used to say something expected or correct:


            There should be an old city hall building here.

            Everybody should arrive by 6 p.m.




            We should be there this evening.


Use of Must


Must doesn’t change its form, whatever be its tense or the number and person of its subject. It can refer to the present or future.


            You must do this now. (Present)

            He must pay damages. (Future)

            You must file a petition. (Future)


Must can refer to the past only when it is used with the present perfect of the main verb.


            She must have gone home. (Here must refers to the past time because it is used with the present perfect of the verb go.)


            She must have reached home. (Past)


Uses of must


Must is used to express ideas such as compulsion, obligation or duty. It is much stronger than should.


            We must love our country.

            They must recognize our rights.

            He must pay the fine.


Must can be used to talk about necessity.


            We must get up early.

            I must improve my writing skills.


            Must we go now?


Must can express probability or logical certainty.


            She must have already left.

            He must be mad to do this.

            Oh, there is the door bell; that must be the postman.


To signify strong determination


            I must go now, whatever happens.


Use of Ought


Ought is different from other auxiliary verbs: it is followed by a to-infinitive.


Uses of ought


Ought expresses ideas such as duty, necessity and moral obligation. It is not as forceful as must, but it is stronger than should.


            You ought to be punctual.

            We ought to help the poor.

            You ought to visit your friends once in a while.


Ought generally points to present and future time. It can point to past time when it is followed by the perfect infinitive (have + past participle).




You ought to have helped him. (It was your duty to help him but you didn’t.)


Uses of Used to


         The auxiliary verb construction used to is used to express an action that


took place in the past, perhaps customarily, but now that action no longer customarily takes place:


     We used to take long vacation trips with the whole family.



The spelling of this verb is a problem for some people because the "-ed" ending quite naturally disappears in speaking: "We yoostoo take long trips." But it ought not to disappear in writing. There are exceptions, though. When the auxiliary is combined with another auxiliary, did, the past tense is carried by the new auxiliary and the "-ed" ending is dropped. This will often happen in the interrogative:


       Didn't you use to go jogging every morning before breakfast?


       It didn't use to be that way.


Used to can also be used to convey the sense of being accustomed to or familiar with something:


      The tire factory down the road really stinks, but we're used to it by now.


      I like these old sneakers; I'm used to them.


Used to is best reserved for colloquial usage; it has no place in formal or academic text.




Uses of Dare


Dare is used both as a principal verb and as an auxiliary verb.


Dare as a principal verb


As a principal verb dare is used in the sense of defy, challenge or face boldly. Note that the principal verb dare is followed by an infinitive with to. It also has forms like dares or dared.


She dared to swim across the river.

How does he dare to do it?


Dare as an auxiliary verb


The auxiliary verb dare is followed by an infinitive without to. The auxiliary dare is common in questions and negative sentences. It doesn’t have forms like dares or dared.

Questions and negatives are made without do.


He dare not do so. (NOT He dares not do so.)

She dare not take such a risk. (NOT She dares not to take such a risk.)

Dare she say that to him?

How dare he do such a thing?




The expression I dare say is no longer used with its original force. It now merely means ‘perhaps’.




I dare say he will agree to our proposal. (=Perhaps, he will agree to our proposal.) I dare say that she is correct. (=Perhaps she is correct.)


List of modals

Here is a list of modals:




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