English Grammar

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CHAPTER 10.  MODAL VERBS

There are nine modal verbs in English: can, could, may, might, must, shall, should, will, and would. Two of these, will and would, have already been discussed in detail.

 

1. Formation of the modal conjugations

All of the modal verbs are used as auxiliaries, and all of them form conjugations in the same way. Thus, the other modal auxiliaries form conjugations in the same way as will and would. For instance, the conjugation of the modal auxiliary could with the verb to work is formed as follows:

Conjugations of the modal auxiliary Could with the verb To Work


SimpleContinuous
  I could work  I could be working
  you could work  you could be working
  he could work  he could be working
  she could work  she could be working
  it could work  it could be working
  we could work  we could be working
  they could work  they could be working
   
PerfectPerfect Continuous
  I could have worked  I could have been working
  you could have worked  you could have been working
  he could have worked  he could have been working
  she could have worked  she could have been working
  it could have worked  it could have been working
  we could have worked  we could have been working
  they could have worked  they could have been working


The formation of conjugations using the modal auxiliaries can be summarized as follows:

ConjugationAuxiliaryVerb Form
  Simple  modal auxiliary  bare infinitive
  Continuous  modal auxiliary + be  present participle
  Perfect  modal auxiliary + have  past participle
  Perfect Continuous  modal auxiliary + have been  present participle


Verbs in the Simple conjugation with a modal auxiliary generally refer to present or future time; whereas verbs in the Perfect conjugation with a modal auxiliary generally refer to past time.

Verbs in the Continuous conjugation with a modal auxiliary generally refer to continuous, ongoing actions in present or future time; whereas verbs in the Perfect Continuous conjugation with a modal auxiliary generally refer to continuous, ongoing actions in past time.

The word order for questions and negative statements in the conjugations with the modal auxiliaries is similar to that in other English conjugations.

a. Questions
To form a question, the first auxiliary is placed before the subject. For example:

Affirmative StatementQuestion
  She can work.  Can she work?
  He would be working.  Would he be working?
  They should have worked.  Should they have worked?
  I could have been working.  Could I have been working?


See Exercise 1.

b. Negative statements
To form a negative statement, the word not is placed after the first auxiliary. It should be noted that the auxiliary can, followed by not, is written as a single word. For example:

Affirmative StatementNegative Statement
  She can work.  She cannot work.
  He would be working.  He would not be working.
  They should have worked.  They should not have worked.
  I could have been working.  I could not have been working.


See Exercise 2.

In spoken English, the following contractions may be used:

Without ContractionsWith Contractions
  cannot  can't
  could not  couldn't
  might not  mightn't
  must not  mustn't
  shall not  shan't
  should not  shouldn't
  will not  won't
  would not  wouldn't

However, it should be noted that the contractions mightn't and shan't are rarely used in modern American English.

c. Negative questions
To form a negative question, the first auxiliary is placed before the subject, and the word not is placed after the subject. However, when contractions are used, the contracted form of not follows immediately after the auxiliary. For example:

Without ContractionsWith Contractions
  Can she not work?  Can't she work?
  Would he not be working?  Wouldn't he be working?
  Should they not have worked?  Shouldn't they have worked?
  Could I not have been working?  Couldn't I have been working?


See Exercise 3.

d. Tag questions
Tag questions are formed using the first auxiliary. In the following examples, the negative tag questions are underlined.

Affirmative StatementAffirmative Statement with Tag Question
  She can work.  She can work, can't she?
  He would be working.  He would be working, wouldn't he?
  They should have worked.  They should have worked, shouldn't they?
  I could have been working.  I could have been working, couldn't I?

 

2. Relationships among the modal auxiliaries

Just as would can be used as the past of will; could can be used as the past of can; might can be used as the past of may; and should can be used as the past of shall. The auxiliary must can refer either to the present or to the past. These relationships among the modal auxiliaries can be summarized as follows:

PresentPast
  can  could
  may  might
  must  must
  shall  should
  will  would


The following examples illustrate these relationships:

Tense of Verb in Main ClauseComplete Sentence
  Simple Present  I think I can do it.
  Simple Past  I thought I could do it.
   
  Simple Present  He predicts it may rain.
  Simple Past  He predicted it might rain.
   
  Simple Present  She knows she must be there.
  Simple Past  She knew she must be there.
   
  Simple Present  I wonder what we shall do tomorrow.
  Simple Past  I wondered what we should do the next day.


See Exercises 4 and 5.

Each of the modal auxiliaries has more than one meaning. The meaning depends upon the context in which the auxiliary is used.

 

3. Can and Could

The modal auxiliary can is most often used in the Simple conjugation.

The most important meaning of can and could is to be able to.
e.g. He can walk thirty miles a day.
      When she was young, she could swim across the lake.
The first example has the meaning, He is able to walk thirty miles a day. The second example has the meaning, When she was young, she was able to swim across the lake.

Like the auxiliary would, could can be used in polite requests and suggestions.
e.g. Could you please tell me how to get to Almond Street?
      You could try asking the bus driver to help you.

As indicated in the previous chapter, could can be used in sentences expressing wishes.
e.g. He wished he could visit France.
      I wish I could have helped you.

See Exercise 6.

It has also been pointed out that could can be used in either the main clause or the subordinate clause of a statement expressing a false or improbable condition.
e.g. If he were stronger, he could help us push the car out of the snow.
      She could have caught the bus if she had left right away.
      I would be glad if I could help you.
      If he could have solved the problem, he would have felt happier.

See Exercises 7 and 8.

In informal English, can is often used with the meaning to be allowed to.
e.g. He says I can take the day off.
      Can I have some more soup?

However, in formal English, it is considered more correct to use the auxiliary may in such situations.
He says I may take the day off.
May I have some more soup?

 

4. May, Might and Must

One of the meanings of may and might is to be allowed to.
e.g. The members of the organization agree that I may join it.
      The members of the organization agreed that I might join it.

The auxiliary must is a stronger form of may and might. One of the meanings of must is to be obliged to or to have to.
e.g. You must provide proper identification in order to cash a check.
      They must work harder if they are to succeed.

It should be noted that the meaning of must not is to be obliged not to.
e.g. You must not leave.
      He must not speak.
The first example has the meaning, You must stay. The second example has the meaning, He must be silent.

In order to express the idea of not being obliged to do something, an expression such as not to be obliged to or not to have to is generally used.
e.g. You do not have to leave.
      He is not obliged to speak.
The first example has the meaning, You may stay, if you wish. The second example has the meaning, He may be silent, if he wishes.

Like could and would, might can be used in polite requests and suggestions. The auxiliaries could, would and might can be used to express differing degrees of politeness:

Degree of PolitenessAuxiliary
  somewhat polite  could
  quite polite  would
  very polite  might

Thus, might expresses the highest degree of politeness.
e.g. Might I observe what you are doing?
      Might I offer some advice?

See Exercise 9.

May, might and must are also used to express differing degrees of probability:

Degree of ProbabilityAuxiliary
  somewhat probable  may, might
  highly probable  must

For instance, may and might are often used in the Simple conjugation to express the idea that an event is somewhat probable.
e.g. You might be right.
      It may snow later this afternoon.

Similarly, must can be used in the Simple conjugation to express the idea that an event is highly probable.
e.g. He must be mistaken.

In the following examples, the Perfect conjugations with may, might and must are used to express differing degrees of probability relating to past events.
      Rupert might have taken the money, but it seems unlikely.
      It is possible he may have called while we were out.
      It must have rained last night, because the streets are wet.

See Exercise 10.

 

5. Should

In British English, the Simple conjugation with the auxiliary should is often used in subordinate clauses stating conditions. This construction is usually used to refer to events that may occur by chance.
e.g. If I should see him, I will tell him what I think.

Should is also used with the meaning ought to. This is the most common use of should in American English.
e.g. You should take an umbrella with you, in case it starts to rain.
      I should answer his letter as soon as possible.

Ought is said to be a defective verb, since it has no infinitive, or present or past participle. It does not modify, but has the same form, regardless of the subject. Ought can be used only in combination with other verbs. Unlike the modal auxiliaries, which are followed by the bare infinitive, ought is followed by the infinitive of whatever verb it accompanies.

In each of the following examples, ought is underlined, and the infinitive which follows it is printed in bold type.
e.g. You ought to take an umbrella with you.
      He ought to stop smoking.
      They ought to drive more carefully.

 

6. Expressions which are synonymous with the modal auxiliaries

The modal verbs can be used only as auxiliaries; they cannot be used on their own. They are defective, since they have no infinitive, or present or past participle.

It should be noted that in addition to the modal auxiliaries will and can, there are two other English verbs, to will and to can, which are conjugated regularly. The verb to will has the meaning to direct one's willpower toward something, or to bequeath by means of a will. The verb to can has the meaning to put into a can.

Because the modal auxiliaries are defective, they cannot be combined with one another. Thus, the fact that the English future tenses are formed with the modal auxiliaries will and shall means that the other modal auxiliaries cannot be put into the future.

When it is desired to put the ideas expressed by the modal auxiliaries into the future, synonymous expressions must be used. The following are the synonymous expressions most often used:

Modal AuxiliarySynonymous Expression
  can  be able to
  may  be allowed to
  must  have to

It should be noted that the expression be allowed to is synonymous with may only when may is used in the sense of permission being granted.

The following examples illustrate how synonymous expressions may be used when it is desired to put the modal auxiliaries can, may and must into the future.

PresentFuture
  I can work.  I will be able to work.
  You may work.  You will be allowed to work.
  He must work.  He will have to work.


See Exercise 11.

a. The pronunciation of Have To
The following table illustrates how the pronunciation of the words have and has in the expression have to differs from the usual pronunciation of the verb to have. In the expression have to, the consonant preceding the t of to is unvoiced. An imitated pronunciation of has and have is indicated in the right-hand column.

Usual pronunciation of Have

ExampleImitated Pronunciation
  She has two children.  "haz"
  We have two children.  "hav"


Pronunciation of Have in the expression Have To

ExampleImitated Pronunciation
  She has to leave.  "hass"
  We have to leave.  "haff"

 

7. The use of auxiliaries in tag questions, short answers and ellipsis

In English, the verbs used as auxiliaries are to be, to do, to have, and the modal auxiliaries. All of these auxiliaries can be used in tag questions and short answers.

a. Negative tag questions
Negative tag questions have already been discussed. An affirmative statement is often followed by a negative tag question, in order to ask for confirmation of the affirmative statement. In the following examples, the negative tag questions are underlined. Contractions are usually used in negative tag questions.
e.g. You are coming with me, aren't you?
      You like coffee, don't you?

For the Simple Present and the Simple Past of the verb to be, tag questions are formed using the verb itself. For instance, in the following examples, the verbs is and were are used in negative tag questions.
e.g. She is very nice, isn't she?
      They were ready on time, weren't they?

For the Simple Present and the Simple Past of verbs other than the verb to be, the auxiliary to do is used in tag questions. For instance, in the following examples, the auxiliaries does and did are used in negative tag questions.
e.g. He rides a bicycle, doesn't he?
      They ordered pizza, didn't they?

For all other tenses and conjugations, the first auxiliary is used in tag questions. For instance, in the following examples, the first auxiliaries have, would, should and can are used in negative tag questions.
e.g. You have worked all night, haven't you?
      He would have helped us, wouldn't he?
      They should get more exercise, shouldn't they?
      She can speak five languages, can't she?

See Exercise 12.

b. Affirmative tag questions
A negative statement is often followed by an affirmative tag question, in order to ask for confirmation of the negative statement, or in order to ask for more information. In the following examples, the affirmative tag questions are underlined.
e.g. He is not very tall, is he?
      They don't want to work, do they?

The rules for forming affirmative tag questions are similar to those for forming negative tag questions. In the case of the Simple Present and Simple Past of the verb to be, the verb itself is used; and in the case of all other tenses and conjugations, the first auxiliary is used.
e.g. He wasn't much help, was he?
      They didn't want to come with us, did they?
      You hadn't slept well, had you?
      She can't speak Greek, can she?
      They wouldn't mind helping us, would they?

See Exercise 13.

c. Short answers
Sometimes it is possible to reply to a question by means of a short answer, consisting of a subject, followed by the verb or first auxiliary used in the question. The rules for forming affirmative and negative short answers are similar to those for forming affirmative and negative tag questions. Thus, in the case of the Simple Present and Simple Past of the verb to be, the verb itself is used; and in the case of all other tenses and conjugations, the first auxiliary is used.

The following are examples of questions with affirmative and negative short answers. The verbs and auxiliaries are underlined.

Contractions are usually used in negative short answers.

QuestionAffirmative Short AnswerNegative Short Answer
  Is he ready?  Yes, he is.  No, he isn't.
  Were you finished?  Yes, I was.  No, I wasn't.
  Do you know them?  Yes, I do.  No, I don't.
  Did we win?  Yes, we did.  No, we didn't.
  Has he left?  Yes, he has.  No, he hasn't.
  Will they need help?  Yes, they will.  No, they won't.
  Could you help me?  Yes, I could.  No, I couldn't.


It should be noted that the form of the verb in a short answer is not always the same as the form of the verb in the question, since the verb of a short answer must agree with its subject. In the following examples, the verbs are underlined, and their subjects are printed in bold type.
e.g. Are you ready? Yes, I am.
      Were you excited? Yes, I was.

See Exercises 14 and 15.

d. Ellipsis
In English, words can sometimes be omitted from a sentence without changing the meaning of the sentence. The words which are omitted are said to be "understood". This type of short form is usually referred to as ellipsis.

Short answers are one kind of ellipsis. For instance, in the example:
      Can you speak Spanish? Yes, I can.
the short answer Yes, I can, means Yes, I can speak Spanish. The words speak Spanish are understood.

Another kind of ellipsis uses the words and so, followed by the verb or first auxiliary, followed by the subject.

For instance, the sentence:
      He can speak Spanish, and I can speak Spanish too.
would normally be shortened to:
      He can speak Spanish, and so can I.

Other examples of this type of ellipsis are given below. The verbs and auxiliaries are underlined.

Without Ellipsis: She is tired, and I am tired too.
With Ellipsis: She is tired, and so am I.

Without Ellipsis: They like ice cream, and we like ice cream too.
With Ellipsis: They like ice cream, and so do we.

Without Ellipsis: He wrote a letter, and I wrote a letter too.
With Ellipsis: He wrote a letter, and so did I.

Without Ellipsis: You had worked all night, and I had worked all night too.
With Ellipsis: You had worked all night, and so had I.

Without Ellipsis: You should get more sleep, and we should get more sleep too.
With Ellipsis: You should get more sleep, and so should we.

As illustrated above, the rules for forming the construction with and so are similar to the rules for forming tag questions and short answers. Thus, in the case of the Simple Present and Simple Past of the verb to be, the verb itself is used; in the case of the Simple Present and Simple Past of verbs other than the verb to be, the auxiliary to do is used; and in the case of all other tenses and conjugations, the first auxiliary is used.

See Exercise 16.

The construction using the words and so is used to express an affirmative idea, following an affirmative statement.

In contrast, a similar construction, using the words and neither, is used to express a negative idea, following a negative statement.

For instance, the sentence:
      He cannot speak Danish, and I cannot speak Danish either.
would normally be shortened to:
      He cannot speak Danish, and neither can I.

Other examples of this type of ellipsis are given below. The verbs and auxiliaries are underlined.

Without Ellipsis: She is not ready, and you are not ready either.
With Ellipsis: She is not ready, and neither are you.

Without Ellipsis: They do not own a car, and he does not own a car either.
With Ellipsis: They do not own a car, and neither does he.

Without Ellipsis: We have not forgotten, and she has not forgotten either.
With Ellipsis: We have not forgotten, and neither has she.

Without Ellipsis: They couldn't find it, and we couldn't find it either.
With Ellipsis: They couldn't find it, and neither could we.

See Exercise 17.

 

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