Modal auxiliary verbs

Modal Auxiliary Verbs

Modal verbs are a kind of auxiliary verb. They facilitate the main verb for suggesting potential, expectation, permission, ability, possibility, and obligation.

When used with the main verb, modal verbs do not end with -s for the third-person singular.  Modal auxiliary verbs never change form, but they have a different form for past tense.

The modal auxiliaries include:

Present Tense Past Tense
  • Will
  • Can
  • Must (have to)
  • May
  • Should (ought to) (had better)
  1. Would (used to)
  2. Could
  3. (Had to)
  4. Might
  5. Should (ought to)

NB: The words in parentheses ( ) are semi-modals. They have the same meaning, but they are different grammatically.

Will – Would

Will indicates a ‘willingness’ to do something in the future. The negative form of willwill not (won’t) indicates an ‘unwillingness’ (refusal, reluctance) to do something.


  • I will give you another opportunity.
  • I will play tomorrow.
  • They will arrive at 10 AM.
  • She won’t come today.

Would indicates general or repeated willingness in the past. It also indicates preference in the present.  


  • If you did not leave, I would still be taking care of you.
  • Whenever I had to go there, they would throw a party.
  • We thought that people would buy this book.
  • If I were you, I would not do it.

Helping and Modal Auxiliary Verbs

Helping verbs or auxiliary verbs such as will, shall, may, might, can, could, must, ought to, should, would, used to, need are used in conjunction with main verbs to express shades of time and mood.

The combination of helping verbs with main verbs creates what are called verb phrases or verb strings.

In the following sentence, “will have been” are helping or auxiliary verbs and “studying” is the main verb; the whole verb string is underlined:

  • As of next August, I will have been studying chemistry for ten years.

Students should remember that adverbs and contracted forms are not, technically, part of the verb. In the sentence, “He has already started.

” the adverb already modifies the verb, but it is not really part of the verb.

The same is true of the 'nt in “He hasn't started yet” (the adverb not, represented by the contracted n't, is not part of the verb, has started).

Shall, will and forms of have, do and be combine with main verbs to indicate time and voice. As auxiliaries, the verbs be, have and do can change form to indicate changes in subject and time.

  • I shall go now.
  • He had won the election.
  • They did write that novel together.
  • I am going now.
  • He was winning the election.
  • They have been writing that novel for a long time.
In England, shall is used to express the simple future for first person I and we, as in “Shall we meet by the river?” Will would be used in the simple future for all other persons. Using will in the first person would express determination on the part of the speaker, as in “We will finish this project by tonight, by golly!” Using shall in second and third persons would indicate some kind of promise about the subject, as in “This shall be revealed to you in good time.” This usage is certainly acceptable in the U.S., although shall is used far less frequently. The distinction between the two is often obscured by the contraction 'll, which is the same for both verbs. In the United States, we seldom use shall for anything other than polite questions (suggesting an element of permission) in the first-person:

  • “Shall we go now?”
  • “Shall I call a doctor for you?”

(In the second sentence, many writers would use should instead, although should is somewhat more tentative than shall.) In the U.S., to express the future tense, the verb will is used in all other cases. Shall is often used in formal situations (legal or legalistic documents, minutes to meetings, etc.) to express obligation, even with third-person and second-person constructions:

  • The board of directors shall be responsible for payment to stockholders.
  • The college president shall report financial shortfalls to the executive director each semester.”

Should is usually replaced, nowadays, by would. It is still used, however, to mean “ought to” as in

  • You really shouldn't do that.
  • If you think that was amazing, you should have seen it last night.

In British English and very formal American English, one is apt to hear or read should with the first-person pronouns in expressions of liking such as “I should prefer iced tea” and in tentative expressions of opinion such as

  • I should imagine they'll vote Conservative.
  • I should have thought so.
See also:  Will commercial companies be the next to take on space travel?
In the simple present tense, do will function as an auxiliary to express the negative and to ask questions. (Does, however, is substituted for third-person, singular subjects in the present tense. The past tense did works with all persons, singular and plural.)

  • I don't study at night.
  • She doesn't work here anymore.
  • Do you attend this school?
  • Does he work here?

These verbs also work as “short answers,” with the main verb omitted.

  • Does she work here? No, she doesn't work here.

With “yes-no” questions, the form of do goes in front of the subject and the main verb comes after the subject:

  • Did your grandmother know Truman?
  • Do wildflowers grow in your back yard?

Forms of do are useful in expressing similarity and differences in conjunction with so and neither.

  • My wife hates spinach and so does my son.

Modals and auxiliary verbs in English

  • Historically, the modals of English, which are listed in (1), derive
    from a special class of verbs in Germanic (the ancestor of English and the
    other Germanic languages).
  • (1) can, could, may, might, must, shall, should, will, would

Modals have always differed from ordinary verbs in Germanic, and in
the course of the history of English, they have diverged from verbs even
further, to the point where they now belong to a syntactic category of
their own. Because many modals have meanings that are often expressed
in other languages by verbal inflections, this syntactic category is
called I(nflection).

In what follows, we review the ways that modals differ from verbs in
English, both morphologically (what forms they exhibit) and syntactically
(how they combine in sentences).

Range of forms

Modals and verbs differ in the range of forms that they exhibit.
English verbs appear in a number of distinct forms (see Finiteness),
whereas modals have a single, invariant form. Modals never end in
-s, even in sentences with third person singular subjects.

(2) a. * She { can-s, may-s } play the piano.
b. She { can, may } play the piano.

Modals also lack productive past tense forms. It is true that
could, might, should, and would originated
in Germanic as past tense forms of can, may, shall,
and will. But today, only could can serve as the past
tense of can, and that only in certain contexts.1


Potential paraphrase

(3) a. Nowadays, you can get one for a dollar. = … it is possible to get one …
b. Back then, you could get one for a nickel. = … it was possible to get one …
(4) a. We can go there tomorrow. = It is possible for us to go there …
b. We could go there tomorrow. =/= It was possible for us to go there …
(5) a. You may ask the boss. = You are allowed to ask the boss.
b. You might ask the boss. =/= You were allowed to ask the boss.
(6) a. Shall I pick up some bread? = Is it a good idea for me to pick up some bread?
b. Should I pick up some bread? =/= Was it a good idea for me to pick up some bread?

Finally, modals lack present and past participles; the missing forms must be

(7) a. * { Cann-ing, may-ing } play the piano pleases her greatly.
b. { Being able, being allowed } to play the piano pleases her greatly.
(8) a. * She has { cann-ed, may-ed } play the piano.
b. She has { been able, been allowed } to play the piano.

Nonfinite contexts

#1 Grammar and Spell checker

A modal is a type of auxiliary (helping) verb that is used to express: ability, possibility, permission or obligation. Modal phrases (or semi-modals) are used to express the same things as modals, but are a combination of auxiliary verbs and the preposition to. The modals and semi-modals in English are:

  1. Can/could/be able to
  2. May/might
  3. Shall/should
  4. Must/have to
  5. Will/would

Can, Could, Be Able To

Can, could and be able to are used to express a variety of ideas in English:

Ability/Lack of Ability

Present and Future:

can/can’t + base form of the verb

  1. Tom can write poetry very well.
  2. I can help you with that next week.
  3. Lisa can’t speak French.

am / is / are / will be + able to + base form of the verb
am not/ isn’t / aren’t/ won’t be + able to + base form of the verb

  1. Mike is able to solve complicated math equations
  2. The support team will be able to help you in about ten minutes.
  3. I won’t be able to visit you next summer.


could / couldn’t + base form of the verb

  1. When I was a child I could climb trees.
  • was / were + able to + base form of the verb
    wasn’t / weren’t + able to + base form of the verb
  • hasn’t / haven’t + been able to + base form of the verb
  1. I wasn’t able to visit her in the hospital.
  2. He hasn’t been able to get in touch with the client yet.

Note: Can and could do not take an infinitive (to verb) and do not take the future auxiliary will.

  • Incorrect: I can to help you this afternoon.
  • Correct: I can help you this afternoon.
  • Correct: I will (I’ll) be able to help you this afternoon.

Possibility / Impossibility

can / can’t + base form of the verb

  1. You can catch that train at 10:43.
  2. He can’t see you right now. He’s in surgery.

could + base form of the verb

  1. I could fly via Amsterdam if I leave the day before.

Ask Permission / Give Permission

Can + Subject + base form of the verb (informal)

  1. Can you lend me ten dollars?

Can + base form of the verb (informal)

Could + subject + base form of the verb (polite)

  1. Could I have your number?
  2. Could I talk to your supervisor please?

Make a suggestion – To make a suggestion use:

Could + base form of the verb (informal)

  1. You could take the tour of the castle tomorrow.

Exercises: Can, Could, Be able to

Fill in the correct form of can, could or be able to as in the examples.

  1. Ben could not help his little brother with his homework yesterday.
  2. Can I call you later tonight?
  1. _______ Tony run long distances when he was a boy?
  2. ______ you please call a tow truck for me? My car broke down. (polite)

Modal auxiliary verbs

Modal auxiliary verbs express meanings such as obligation, possibility, necessity, etc., which reflect somebody's (often the writer's) attitudes towards the state, event, etc. expressed by the verb phrase.

Often, it is difficult to pinpoint the exact type of meaning conveyed by a modal auxiliary, as different types of meaning may be present simultaneously.

For example, among other things, the modal can may be used to express ability and possibility, as in the following examples:

(1) Bill can swim. (i.e. 'Bill has the ability to swim')

(2) The door can only be opened with a special key. (i.e. 'it is only possible to open the door with a special key')

Fairly often, however, it is difficult to claim that only one of these meaning is expressed:

(3) I can drive you to the airport tomorrow. ('I have the ability to drive you, e.g.  because I have a driver's licence' or 'It is possible for me to drive you, e.g. because I am free at the appropriate time')

Grammatical properties of modal auxiliaries

In addition to the the properties shared by all auxiliaries, modals are characterized by the following:

  • Modals have no non-finite forms (i.e. they have no infinitival or participial forms).
  • Modals have no inflected forms in the present tense (in particular, they have no 3rd person -s ending).

"Primary Auxiliaries And Modal Auxiliaries Verbs"

Stage 6 Stage 7

This week’s blog is based on auxiliary verbs. In English there are two types of auxiliary verb, primary auxiliaries and modal auxiliaries.
The three primary auxiliary verbs are ‘be’, ‘have’ and ‘do’. There are ten common modal auxiliary verbs and they are ‘can’, ‘could’, ‘will’, ‘would’, ‘shall’, ‘should’, ‘may’, ‘might’, ‘must’ and ‘ought’.

Modal auxiliary verbs often express the ideas of necessity and possibility.

Download Exercise

We use the primary auxiliary ‘do’ for the present simple and the past simple and we generally only use it in questions and negative sentences. It isn’t commonly used in positive sentences. For example we say «do you have a pen, please?» «Yes, I have a pen» or «no, I don’t have a pen». «Does he play football»? «Yes he plays football» or «no, he doesn’t play football».

We use the primary auxiliary ‘have’ to form the perfect tenses. We say «I have eaten some chocolate» or «he has been to Sevilla». We could also say «I have been sitting here for ten minutes». Remember each perfect tense has a different use.

For example we use the present perfect when we are thinking about the time before and up to now, we use the past perfect when we are thinking about the time before and up to a point in the past and we use the future perfect when we are thinking about the time before and up to a point in the future.

We use the perfect continuous tenses to communicate the duration of an action up to a point in time.

The primary auxiliary ‘be’ is used to form the continuous tenses and the passive voice. For example we say «I am speaking to you now», which is a sentence in the present continuous.

In the passive voice the verb ‘be’ tells us when the action happened.

For example if I say, «the window is being opened by him» we know that the action is happening now because the verb ‘be’ is in the present continuous tense.

Modal auxiliaries are used to express necessity and possibility. When we say «I could be free at seven o’ clock this evening», it means there is a possibility that I will be free at seven o’ clock this evening.

If I say «you must study, if you want to pass the exam», it communicates that there is a necessity for you to study in order to pass the exam.

We use the modal auxiliary ‘can’ to communicate the ability to do something, for example «I can speak English». When we use the first conditional tense and say, for example, «you can go out to play with your friends, if you eat all your dinner», we are expressing the possibility of being allowed outside to play on the condition that first you eat all your dinner.

We use ‘shall’ when we are making a suggestion with the pronouns ‘I’ and ‘we’, instead of using the auxiliary ‘will’. For example we say «shall we go for a walk»? «Shall I take the rubbish out»? We can also use ‘shall’ to ask for a suggestion, for example «where shall we go this weekend?»

We can use ‘should’ to communicate probability. For example if we say «he should be in the office», it means there is a probability that he is in his office. We can also use ‘ought’ instead of ‘should’ because they mean the same thing, but we follow ‘ought’ with the infinitive with ‘to’. For example «I ought to finish my homework».

‘May’ and ‘might’ express possibility too. If we say «he might be from England», it means he is possibly from England. If we say «she may have gone home», it means that there is a possibility she has gone home.

The auxiliary ‘will’ is used to express the future. For example «I will take the exam today». We use the auxiliary ‘would’ in conditional sentences. For example «if I went to the beach, I would swim in the sea».

Remember that after an auxiliary verb we use the infinitive without ‘to’, except the auxiliary ‘ought’. For example we say «I must go», not «I must to go», but we say «I ought to watch the film», not «I ought watch the film».

Practise using primary and modal auxiliaries.
  • G. Harman
  • Download Exercise

Modal Auxiliary Verbs

During the small hours, tipsy Maurice became an oracle, ambiguous, wayward, but impressive. Even his voice changed a little. He told the sombre truths of the lighthearted, betraying in a casual hour what was never intended to be shown.

If the tide was low the two of them watched the gleams on the foreshore, at half tide they heard the water chuckling, waiting to lift the boats, at flood tide they saw the river as a powerful god, bearded with the white foam of detergents, calling home the twenty-seven lost rivers of London, sighing as the night declined.

  • ‘Maurice, ought I to go away?’
  • ‘You can’t.’
  • ‘You said you were going to go away yourself.’

‘No-one believed it. You didn’t. What do the others think?’

‘They think your boat belongs to Harry.’

‘Nothing belongs to Harry, certainly all that stuff in the hold doesn’t. He finds it easier to live without property. As to Maurice, my godmother gave me the money to buy a bit of property when I left Southport.’

‘I’ve never been to Southport.’

‘It’s very nice. You take the train from the middle of Liverpool, and it’s the last station, right out by the seaside.’

  1. ‘Have you been back since?’
  2. ‘No.’
  3. ‘If Maurice belongs to you, why do you have to put up with Harry?’
  4. ‘I can’t answer that.’
  5. ‘What will you do if the police come?’
  6. ‘What will you do if your husband doesn’t?’

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