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Fundamentals of English Grammar - Chapter 7: Modal Auxiliaries

7-1 The Form of Modal Auxiliaries

The verbs listed below are called "modal auxiliaries." They are helping verbs that express a wide range of meanings (ability, permission, possibility, necessity, etc.). Most of the modals have more than one meaning.

  • Auxiliary + the Simple Form of a Verb
    can: (a) Olga can speak English.
    could: (b) He couldn't come to class.
    may: (c) It may rain tomorrow.
    might: (d) It might rain tomorrow.
    should: (e) Mary should study harder.
    had better: (f) I had better study tonight.
    must: (g) Billy! You must listen to me!
    will: (h) I will be in class tomorrow.
    would: (i) Would you please close the door?

    Can, could, may, might, should,had better, must, will, and would are immediately followed by the simple form of a verb.

    • They are not followed by to.
      INCORRECT: Olga can to speak English.
    • The main verb does not have a final -s.
      INCORRECT: Olga can speaks English.
    • The main verb is not in a past form.
      INCORRECT: Olga can spoke English.
    • The main verb is not in its -ing form.
      INCORRECT: Olga can speaking English.
  • Auxiliary + to + the Simple Form of a Verb
    have to: (i) I have to study tonight.
    have got to: (k) I have got to study tonight.
    Be able to: (l) Kate is able to study harder.
    ought to: (m) Kate ought to study harder.

    To + the simple form is used with these auxiliaries:
    have to, have got to, be able to, and ought to.

7-2 Expressing Ability: Can and Could

  • (a) Bob can play the piano.
    (b) You can buy a screwdriver at a hardware store.
    (c) I can meet you at Ted's tomorrow afternoon.

    Can expresses ability in the present or future.

  • (d) can't / cannot / can not understand that sentence.

    The negative form of can may be written can't, cannot, or can not.

  • (e) I can gó.
    (f) I cán't go.

    In spoken English, can is usually unstressed and pronounced /kǝn/ = "kun."

    Can't is stressed and pronounced /kæn/, with the final sound being a glottal stop.* The glottal stop replaces the /t/ in spoken English. Occasionally native speakers have trouble hearing the difference between can and can't and have to ask for clarification.

  • (g) Our son could walk when he was one year old.

    The past form of can is could.

  • (h) He couldn't walk when he was six months old.

    The negative of could is couldn't or could not.

  • (i) He can read.
    (j) He is able to read.
    (k) She could read.
    (l) She was able to read.

    Ability can also be expressed with a form of be able to.
    Examples (i) and (j) have the same meaning.
    Examples (k) and (l) have the same meaning.

* A glottal stop is the sound you hear in the negative "unh-uh." The air is stopped by the closing of your glottis in the back of your throat. The phonetic symbol for the glottal stop is /?/.

7-3 Expressing Possibility: May, Might, and Maybe; Expressing Permission: May and Can

  • (a) It may rain tomorrow.
    (b) It might rain tomorrow.
    (c) Why isn't John in class? I don't know. He may / might be sick today.

    May and might express possibility in the present or future. They have the same meaning. There is no difference in meaning between (a) and (b).

  • (d) It may not rain tomorrow.
    (e) It might not rain tomorrow.

    Negative: may not and might not
    (Do not contract may and might with not.)

  • (f) Maybe it will rain tomorrow.
    COMPARE:
    (g) Maybe John is sick. (adverb)
    (h) John may be sick. (verb)

    In (f) and (g): maybe (spelled as one word) is an adverb. It means "possibly." It comes at the beginning of a sentence.
    INCORRECT: It will maybe rain tomorrow.

    In (h): may be (two words) is a verb form: the auxiliary may + the main verb be.
    Examples (g) and (h) have the same meaning.
    INCORRECT: John maybe sick.

  • (i) Yes, children, you may have a cookie after dinner.
    (j) Okay, kids, you can have a cookie after dinner.

    May is also used to give permission, as in (i).
    Can is often used to give permission, too, as in (j).

    NOTE: Examples (i) and (j) have the same meaning, but may is more formal than can.

  • (k) You may not have a cookie.
    You can't have a cookie.

    May not and cannot (can't) are used to deny permission (i.e., to say "no").

7-4 Using Could to Express Possibility

(a) How was the movie? Could you understand the English?
-> Not very well. I could only understand it with the help of subtitles.

(b) Why isn't Greg in class?
-> I don't know. He could be sick.

(c) Look at those dark clouds. It could start raining any minute.

One meaning of could is past ability, as in (a).
Another meaning of could is possibility.
In (b): He could be sick has the same meaning as He may/might be sick, i.e., It is possible that he is sick.

In (b): could expresses a present possibility.

In (c): could expresses a future possibility.

7-5 Polite Questions: May I, Could I, Can I

Polite Question

  • (a) May I please borrow your pen?
    (b) Could I please borrow your pen?
    (c) Can I please borrow your pen?

    People us may I, could I,* and can I to ask polite questions. The questions ask for someone's permission or agreement.
    Examples (a), (b), and (c) have basically the same meaning.

    Note: can I is less formal than may I and could I.

  • (d) Can I borrow your pen, please?
    (e) Can I borrow your pen?

    Please can come at the end of the question, as in (d).
    Please can be omitted from the question, as in (e).

Possible Answers

  • Yes.
    Yes. Of course.
    Yes. Certainly.
    Of course.
    Certainly.
    Sure. (informal)
    Okay. (informal)
    Uh-huh (meaning "yes")
    I'm sorry, but I need to use it myself.

7-6 Polite Questions: Would You, Could You, Will You, Can You

Polite Question

  • (a) Would you please open the door?
    (b) Could you please open the door?
    (c) Will you please open the door?
    (d) Can you please open the door?

Possible Answers

  • Yes.
    Yes. Of course.
    Certainly. I'd be happy to.
    Of course. I'd be glad to.
    Sure. (informal)
    Okay. (informal)
    Uh-huh (meaning "yes")
    I'm sorry, I'd like to help, but my hands are full.

People use would you, could you, will you, and can you to ask polite questions. The questions ask for someone's help or cooperation.
Examples (a), (b), (c), and (d) have basically the same meaning.
Would and could are generally considered more polite than will and can.

NOTE: May is NOT used when you is the subject of a polite question.
INCORRECT: May you please open the door?

7-7 Expressing Advice: Should and Ought To

  • (a) My clothes are dirty. I should / ought to wash them.
    (b) INCORRECT: I should to wash them.
    (c) INCORRECT: I ought washing them.

    Should and ought to have the same meaning:
    "This is a good idea. This is good advice."
    FORMS:
    should + simple form of a verb (no to)
    ought + to + simple form of a verb

  • (d) You need your sleep. You should not (shouldn't) stay up late.

    NEGATIVE: should + not = shouldn't
    (Ought to is usually not used in the negative.)

  • (e) A: I'm going to be late for the bus. What should I do?
    -> B: Run!

    QUESTION: should + subject + main verb
    (Ought to is usually not used in questions.)

  • (f) A: I'm tired today.
    -> B: You should/ought to go home and take a nap.

    (g) A: I'm tired today.
    -> B: Maybe you should/ought to go home and take a nap.

    The use of maybe with should and ought to "softens" advice.

    COMPARE:
    In (f): Speaker B is giving definite advice. He is stating clearly that he believes going home for a nap is a good idea and is the solution to Speaker A's problem.
    In (g): Speaker B is making a suggestion: going home for a nap is one possible way to solve Speaker A's problem.

7-8 Expressing Advice: Had Better

  • (a) My clothes are dirty. I should/ought to/had better wash them.
    (d) You're driving too fast! You'd better slow down.

    Had better has the same basic meaning as should and ought to: "This is a good idea. This is good advice."

    Had better has more of a sense of urgency than should or ought to. It often implies a warning about possible bad consequences. In (b): If you don't slow down, there could be a bad result. You could get a speeding ticket or have an accident.

  • (c) You'd better not eat that meat. It looks spoiled.

    NEGATIVE: had better not

  • (d) I'd better send my boss an email right away.

    In conversation, had is usually contracted: 'd.

7-9 Expressing Necessity: Have to, Have Got to, Must

  • (a) I have a very important test tomorrow.
    I have to/have got to/must study tomorrow.

    Have to, have got to, and must have basically the same meaning. They express the idea that something is necessary.

  • (b) I'd like to go with you to the movie this evening, but I can't. I have to go to a meeting.
    (c) Bye now! I've got to go. My wife's waiting for me. I'll call you later.
    (d) All passengers must present their passports at customs upon arrival.
    (e) Tommy, you must hold onto the railing when you go down the stairs.

    Have to is used much more frequently in everyday speech and writing than must.
    Have got to is typically used in informal conversation, as in (c).
    Must is typically found in written instructions or rules, as in (d). Adults also use it when talking to younger children, as in (e). It sounds very strong.

  • (f) Do we have to bring pencils to the test?
    (g) Why did he have to leave so early?

    QUESTIONS: Have to is usually used in questions, not must or have got to. Forms of do are used with have to in questions.

  • (h) I had to study last night.

    The PAST form of have to, have got to, and must (meaning necessity) is had to.

  • (i) I have to ("hafta") go downtown today.
    (j) Rita has to ("hasta") go to the bank.
    (k) I've got to ("gotta") study tonight.

    Notice that have to, has to, and have got to are commonly reduced, as in (i) through (k).

7-10 Expressing Lack of Necessity: Do Not Have To; Expressing Prohibition: Must Not

  • (a) I finished all of homework this afternoon. I don't have to study tonight.
    (d) Tomorrow is a holiday. Mary doesn't have to go to class.

    Don't/doesn't have to expresses the idea that something is not necessary.

  • (c) Bus passengers must not talk to the driver.
    (d) Children, you must not play with matches!

    Must not expresses prohibition (DO NOT DO THIS!).

  • (e) You mustn't play with matches.

    Must + not = mustn't
    (NOTE: The first "t" is not pronounced.)

7-11 Making Logical Conclusions: Must

  • (a) A: Nancy is yawning.
    -> B: She must be sleepy.

    In (a): Speaker B is making a logical guess. He bases his guess on the information that Nancy is yawning.
    His logical conclusion, his "best guess," is that Nancy is sleepy. He uses must to express his logical conclusion.

  • (b) LOGICAL CONCLUSION: Amy plays tennis every day.
    She must like to play tennis.
    (c) NECESSITY: If you want to get into the movie theater, you must buy a ticket.

    COMPARE: Must can express

    • a logical conclusion, as in (b).
    • necessity, as in (c).
  • (d) NEGATIVE LOGICAL CONCLUSION: Eric ate everything on his plate except the pickle. He must not like pickles.
    (e) PROHIBITION: There are sharks in the ocean near our hotel. We must not go swimming there.

    COMPARE: Must not can express

    • a negative logical conclusion, as in (d).
    • prohibition, as in (e).

7-12 Tag Questions with Modal Auxiliaries

  • (a) You can come, can't you?
    (b) She won't tell, will she?
    (c) He should help, shouldn't he?
    (d) They couldn't do it, could they?
    (e) We would like to help, wouldn't we?

    Tag questions are common with these modal auxiliaries: can, will, should, could, and would.

  • (f) They have to leave, don't they?
    (g) They don't have to leave, do they?
    (h) He has to leave, doesn't he?
    (i) He doesn't have to leave, does he?
    (j) You had to leave, didn't you?
    (k) You didn't have to leave, did you?

    Tag questions are also common with have to, has to, and had to.
    Notice that forms of do are used for the tag in (f) through (k).

7-13 Giving Instructions: Imperative Sentences

  • COMMAND:
    (a) Captain: Open the door!
    -> Soldier: Yes, sir!
    REQUEST:
    (b) Teacher: Open the door, please.
    -> Student: Sure.
    DIRECTIONS:
    (C) Barbara: Could you tell me how to get to the post office?
    -> Stranger: Certainly. Walk two blocks down this street. Turn left and walk three more blocks. It's on the right-hand side of the street.

    Imperative sentences are used to give commands, make polite requests, and give directions. The difference between a command and a request lies in the speaker's tone of voice and the use of please.

    Please can come at the beginning or end of a request:
    Open the door, please.
    Please open the door.

  • (d) Close the window.
    (e) Please sit down.
    (f) Be quiet!
    (g) Don't walk on the grass.
    (h) Please don't wait for me.
    (i) Don't be late.

    The simple form of a verb is used in imperative sentences. In (d): The understood subject of the sentence is you (meaning the person the speaker is talking to): Close the window = You close the window.
    NEGATIVE FORM:
    Don't + the simple form of a verb

7-14 Making Suggestions: Let's and Why Don't

  • (a) It's hot today. Let's go to the beach.
    -> Okay. Good idea.
    (b) It's hot today. Why don't we go to the beach.
    -> Okay. Good idea.

    Let's and Why don't we are used to make suggestions about activities for you and another person to do.
    Examples (a) and (b) have the same meaning.
    Let's = let us

  • (c) I'm tired.
    -> Why don't you take a nap?
    -> That's a good idea. I think I will.

    In (c): Why don't you is used to make a friendly suggestion or to give friendly advice.

7-15 Stating Preferences: Prefer, Like ... Better, Would Rather

  • (a) I prefer apples to oranges.
    (b) I prefer watching TV to studying.

    prefer + noun + to + noun
    prefer + noun + to + noun

  • (c) I like apples better than oranges.
    (d) I like watching TV better than studying.

    like + noun + better than + noun
    like + -ing verb + better than + -ing verb

  • (e) Ann would rather have an apple than an orange.
    (f) INCORRECT: Ann would rather has an apple.
    (g) I'd rather visit a big city than live there.
    (h) INCORRECT: I'd rather visit a big city than to live there.
    INCORRECT: I'd rather visit a big city than living there.

    Would rather is followed immediately by the simple form of a verb (e.g., have, visit, live), as in (e).
    Verbs following than are also in the simple form, as in (g).

  • (i) I'd / You'd / She'd / He'd / We'd / They'd rather have an apple.

    Contraction of would = 'd'

  • (j) Would you rather have an apple or an orange?

    In (j): In a polite question, would rather can be followed by or to offer someone a choice.

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