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CAN, COULD; MAY, MIGHT; MUST; WILL, WOULD; SHALL, SHOULD; OUGHT
No suffix (-s, -ing, -ed)
He should stay here.
Followed by bare infinitive, EXCEPT OUGHT + TO-infinitive
They may come tonight. You ought to revise regularly.
BEFORE the subject in questions
Can I say something?
Followed by NOT in negations
I couldn’t understand him.
Do NOT have TENSES. Refer to the PRESENT and FUTURE
I must go now . You must call me early tomorrow morning.
Susan can play the guitar. CAN= be able to; ability in the present ABILITY: CAN, COULD, BE ABLE TO When you graduate, you will be able to get a job. WILL BE ABLE TO= ability in the future I haven’t got any money now, but I can pay you tomorrow. (I decide now about something I will do tomorrow) BUT we use CAN when we decide now about something we will do in the near future.
ABILITY: CAN, COULD, BE ABLE TO I could /was able to run fast when I was young . Peter could was able to climb up a tree. COULD= used to be able, ability in the past ( REPEATED action ). Use WAS/WERE ABLE TO with no difference in meaning. Although it was dark, he was able to find his way. WAS/WERE ABLE TO= managed to do, ability in a particular situation in the past (SINGLE action) She listened carefully and she could hear people talking. Normally use COULD with verbs: see, hear, smell, taste, feel, understand, guess, remember In NEGATIONS use COULDN’T or WASN’T/WEREN’T ABLE TO with no difference in meaning: I couldn’t/ wasn’t able to reach him on the phone.
OBLIGATION/ DUTY/ NECESSITY: MUST, HAVE TO, SHOULD, OUGHT TO, NEED We must listen to our teacher. MUST= it is your duty/ you are obliged to do something. Use it to refer to the present or future. You have to wear a seatbelt in a car. HAVE TO= It is necessary to do something MUST when speaker decides that something is necessary. HAVE TO when somebody else has made the decision. I must finish the report by tomorrow. I have to finish the report by tomorrow. BUT in QUESTIONS there is a difference in meaning: MUST I tidy my room? (= do you insist that I tidy my room?) Do I HAVE TO tidy my room? (= is it necessary for me to tidy my room?)
OBLIGATION/ DUTY/ NECESSITY: MUST, HAVE TO, SHOULD, OUGHT TO, NEED I’ve got to go now. It’s very late! HAVE GOT TO has the same meaning as HAVE TO , often used in everyday speech. We had to call for the doctor when Aunt Lucy fainted last night. HAVE TO when you need to use OTHER TENSES. Everyone should/ ought to recycle their rubbish. SHOULD/ OUGHT TO express duty but less emphatic than must. Need I talk to the boss right away? NEED= it is necessary to
ABSENCE OF NECESSITY: NEEDN’T/ DON’T HAVE TO/ DON’T NEED TO/ DIDN’T NEED TO/ NEEDN’T HAVE DONE You needn’t/ don’t have to/ don’t need to work today. NEEDN’T/ DON’T HAVE TO/ DON’T NEED TO+ infinitive (Present of Future)= it isn’t necessary to do something. She didn’t need to/ didn’t have to take a taxi. (It wasn’t necessary, so she didn’t.) DIDN’T NEED TO/ DIDN’T HAVE TO= an action didn’t happen in the past because we knew then that it wasn’t necessary. You needn’t have bought any bread. I’d already bought some. (It wasn’t necessary, but you did.) NEEDN’T + PERFECT INFINITIVE= it wasn’t necessary to do something, but it was done.
PROHIBITION: MUSTN’T/ CAN’T You mustn’t/can’t drive over 60mph. MUSTN’T/CAN’T= it is forbidden to do something/ you are not allowed to do sth/ it is against the rules/ law to do sth PROBABILITY: SHOULD, OUGHT TO It’s ten o’clock. He should be/ ought to be at work. SHOULD/ OUGHT TO= probably. Express that something is likely to happen in the present or future.
LOGICAL ASSUMPTIONS: MUST, CAN’T/COULDN’T It is Sunday. He must be at home . MUST= I’m sure/ certain that something is true. It’s used in affirmative sentences and expresses positive logical assumptions. It is Sunday. He can’t/ couldn’t be at work. CAN’T/ COULDN’T= I’m sure that something isn’t true, real. They’re used in negations and express negative logical assumptions.
POSSIBILITY: CAN, COULD, MAY, MIGHT This road can get very busy. CAN+ present infinitive= general possibility. It’s theoretically possible. Used in affirmative sentences to show that something is possible theoretically or in general, that is, when we are not referring to a specific situation. The roads could/ may/ might get very busy tomorrow afternoon because there is a demonstration. COULD/ MAY/ MIGHT= it’s possible/likely/ perhaps. Used to show that something is likely to happen in a specific situation.
POSSIBILITY: CAN, COULD, MAY, MIGHT I got a bouquet of flowers, but there was no card. Who can/ could/ might they be from? NOTE: In questions we use CAN to talk about general or specific possibility, COULD or MIGHT . We don’t use may . Yesterday, I left the car unlocked. It could/ might have been stolen, but luckily it wasn’t. COULD/ MIGHT+ perfect infinitive. Refers to the past. It was possible, but it didn’t happen.
PERMISSION: CAN/COULD/ MAY/ MIGHT “ Can I use your pen for a minute, please?” “ Of course.” CAN/ COULD/ MAY/ MIGHT I…?= do you/ would you mind if…? Could & May are more polite than can. Might is formal. May & Might are used to ask for permission when we do not know the other person very well. We normally reply with: ‘ Certainly.’/ ‘Of course.’/ ‘Why not?’/ ‘No, I’m afraid you can’t .’ ASKING for permission
PERMISSION: CAN/COULD/ MAY/ MIGHT GIVING permission You may make a phone call here. CAN/ MAY= you are allowed to do something. Can is informal, may is formal. May is usually used in writing. We don’t use could or might to give permission. We don’t use COULD or MIGHT to give permission.
PERMISSION: CAN/COULD/ MAY/ MIGHT REFUSING permission I’m sorry, but you can’t/ mustn’t use the fax. Customers may not enter this area. CAN’T/ MUSTN’T/ MAY NOT= you are not allowed to do something. MAY NOT is formal and is usually used in writing. “ Could I stay a little longer?” “ I’m sorry, but you can’t. ” We don’t use couldn’t to refuse permission.
PERMISSION: CAN/COULD/ MAY/ MIGHT TALKING about permission All citizens over the age of 18 can/ are allowed to vote. CAN/ ALLOWED TO= refer to laws or regulations. NOTE: There is a difference between MAY and BE ALLOWED TO in questions. May I use your phone? (=will you allow me to use your phone?) Are we allowed to use the office phone? (=what is the rule)
PERMISSION: CAN/COULD/ MAY/ MIGHT TALKING about permission I could/was allowed to go to parties when I was young. (in general) I was allowed to go to John’s party last night. ( particular situation) COULD/ WAS/ WERE ALLOWED TO to say that we had general permission to do something in the past. BUT WAS/ WERE ALLOWED TO and not could, to say that we had permission to do something in a particular situation.
REQUESTS: CAN/ COULD/ WILL/ WOULD/ MAY/ MIGHT Can/ Will you get me a glass of water? (informal) Could/ Would you type these letters for me, please? (more polite) CAN/ COULD/ WILL/ WOULD YOU…?= to ask someone to do something for us. WOULD & COULD are more polite than CAN or WILL. We normally reply with: ‘Yes, I’d be happy to.’/ ‘Yes, I’d be glad to.’/ ‘Certainly.’/ ‘Of course.’/ ‘I’m sorry, but I can’t.’ Can/ Could/ May I have a piece of that cake, please? CAN/ MIGHT/ CAN/ COULD= to ask for something politely. MIGHT is formal and is not often used. We normally reply with: ‘Certainly.’/ ‘Yes, certainly.’/ ‘Of course.’/ ‘Yes, of course.’
OFFERS: I’LL/ SHALL/ CAN/ COULD You look tired. I’ll do the ironing for you. I’LL= I’m willing to do something. (informal) Shall/ Can/ Could I give you a hand with the preparations? SHALL/ CAN/ COULD I/we…?= Would you like me/us to…?/ Do you want me/us to…?
SUGGESTIONS: SHALL/ CAN/ COULD “ Shall we go to the theatre tomorrow night?” “ I’d rather not. We can/ could go to the cinema instead.” SHALL I/ WE…?= Why don’t we…?/ How about…? I/ WE CAN/COULD= What about…?/ Let’s… “ Where shall I put these flowers?” “ In this vase.” SHALL= in questions when we are asking for suggestions or instructions.
ADVICE: SHOULD/ OUGHT/ MUST You should always wear a life jacket when you go canoeing. SHOULD/ OUGHT TO+ infinitive= I advise you to/ You had better do something. ‘ You must follow a healthy diet,’ the doctor said to me. (an order which is likely to be obeyed) ‘ You should follow/ ought to follow a healthy diet,’ my friend said to me. (a piece of advice which may or may not be followed) MUST= to give strong advice.
CRITICISM: SHOULD/ OUGHT The owners shouldn’t have left/ ought not to have left the window unlocked. (but you left it unlocked) You should have come/ ought to have come to me for help. (but you didn’t) SHOULD/ OUGHT+ perfect infinitive= it would have been better if you had… We use these structures to criticise someone else’s actions.