MODAL VERBS

(1) Obligation, recommendation, ability

MUST for a necessary action You must keep this door locked. to give someone an order You must be more careful.

to describe a duty Everyone must recycle as much as possible. to make a strong recommendation You really must go and see The History Boys.

to emphasise an intention I must lend you this book. for formal questions (must I, you etc.) Must you go?

HAVE TO / HAS TO for a necessary action We have to be there by six.

for a rule We have to wear a uniform at our school.

have to is the more commonly used question form Do you have to go?

have / has got to can be used informally instead of have to We’ve got to be there by six.

MUST NOT, DO NOT HAVE TO must not describes what is not allowed You mustn’t start until I tell you.

do not have to or have / has not got to describes what is not necessary Tony doesn’t have to go to college.

HAD TO, DIDN’T HAVE TO had to is used as a past form to must Sorry I’m late. I had to stay on at work.

SHOULD, SHOULDN’T (OUGHT TO, OUGHT NOT TO) to make a recommendation You should come to work on your bike. It would be much quicker.

to say what we think is the right thing to do I think you ought to go to the doctor. You look terrible.

to say something is correct or incorrect You shouldn’t write your name at the top of the letter.

in formal writing, should = must, but is more polite All students should report to the examination room by 8.

SHOULD HAVE, SHOULDN’T HAVE (OUGHT TO HAVE, OUGHT NOT TO HAVE) to say that we think that someone has made a mistake or done something wrong

You shouldn’t have put in so much salt.

HAD BETTER (NOT) to make a recommendation, when we say what we think is the right way to do I think you’d better go to the doctor.

BE TO a formal way of saying must in instructions All students are to be respected.

NEED, NEED TO modal verb with no 3rd person and it is used mainly in questions and negatives Do I need to fill in this form?

DIDN’T NEED TO, NEEDN’T HAVE (DONE)

didn’t need to past situation, where something was not necessary, so it was not done Kate looked after the children, so we didn’t need to take them to the nursery.

needn’t have done past situation, where something was done, but it was not necessary I needn’t have gone so early to the office. The meeting was cancelled.

BE ABLE TO, CAN, COULD be able to emphasises that a difficulty has been overcome Harry can’t speak, but he is able to communicate with sign language.

tense forms of be able to are used to make the description of ability more definite than can, or for time references not covered by can/could

I’ll be able to finish this tomorrow. (= I can and will) / I haven’t been able to find the answer yet.

could describes a general past ability Jane could swim 200 metres when she was nine.

was/were I able to describes having the ability and doing something successfully She was able to swim to the rocks and rescue the child.

(2) Possibility, certainty

CAN / COULD to make statements about what is generally possible It can be very cold here in winter.

could past situation In those days, ships could travel for weeks on end without seeing land.

easily + could to emphasise a possibility People could easily fall down these stairs in the dark.

could always to point out a possible choice or decision You could always phone her when we get to the cinema.

when we ask questions about possibility Who can / could that be outside Mr. Smith’s office?

can / could hardly when we think something is impossible It can / could hardly be Jane Thompson. She’s in Berlin this week.

can / could only when we are sure about the answer It can / could only be the new sales manager.

MAY, MIGHT, COULD to describe what is possible in a particular situation This may / might / could be the last time I ever see you.

+well / just to emphasise the possibility; just the possibility = less likely You may well have the answer. / Your plan could just work.

may/might as well there is no reason for not doing something There’s no point waiting for the bus any longer. We might as well start walking.

may/might not for negative possibilities I may / might not have the time to come.

may have, might have, could have possible events in the past Jack is not here yet. He may have missed the train.

might have, could have to show annoyance You might have told me the match was cancelled! I went all the way there for nothing!

might have, could have when shocked because something nearly happened Thank heavens he’s safe! He could have drowned!

CAN’T / COULDN’T BE certainty that something is impossible That definitely can’t be Tom over there. He’s in Canada.

MUST BE certainty that something is true You must be tired after working so hard.

CAN’T / COULDN’T HAVE DONE certainty that something in the past was impossible Helen couldn’t have taken the car. She didn’t have the keys.

with surely emphasis Surely you can’t have carried all these bags on your own.

can’t/couldn’t have been or could/can + hardly/only certainty that something wasn’t true That can’t have been successful.

MUST HAVE DONE certainty that something in the past was true I can’t find my wallet. I must have dropped it in the supermarket.

BE BOUND TO, BE SURE TO, BE CERTAIN TO to describe a future event which we are sure will happen Don’t worry about the exam. You’re sure to pass!

SHOULD, OUGHT TO to describe something we think is probably true, or has failed to happen There should be a turning here!

SHOULD HAVE, OUGHT TO HAVE to describe what we think has probably happened or believe has failed to happen They should have arrived in London by now.

(3) Other uses

CAN/COULD for requests Can/Could you carry this for me? for permission Can/Could I leave early?

to make an offer Can/Could I offer you some tea? to make a suggestion Can/Could I make a suggestion?

CAN’T/CANNOT when something is not allowed You can’t leave your bike here. to emphasise something unbelievable You can’t be serious!

COULD to express surprise How could you waste so much money! for emphasis I’m so unhappy I could cry!

COULDN’T = ‘It doesn’t matter to me at all’ I couldn’t care less what you do. a comparative for emphasis Things couldn’t be better!

MAY for polite requests May I make a suggestion? in be that as it may ... = ‘perhaps that is true but...’ in try as I/you etc. may... formal phrase Try as I may, I just can’t remember.

MIGHT as emphatic form of ‘perhaps I’ll do that’ I might just do that! as emphatic form of ‘although you are...’ You might be older than me, but...

SHALL for an offer Shall I carry that for you? to ask for advice when uncertain What shall we do?

in formal legal language (all persons) The tenant shall be responsible for all repairs.

SHOULDN’T HAVE DONE, NEEDN’T HAVE DONE to express thanks You really shouldn’t have brought me flowers. That’s very kind of you.

WILL/WON’T for an assertion about a result I’ll definitely win! No you won’t! for an offer/agreement I’ll do the washing up.

for a promise I’ll be home by eight. for a threat You’ll be sorry!

WOULD to refer to an annoying habit, typical of a person Jack would say that!

in sentences expressing certainty, where the sentence is a suppressed conditional sentence Nobody would agree with that idea. (if we asked them)

after be followed by adjectives doubtful, unlikely to emphasise a tentative action It’s unlikely that Jim would do something like that.

WOULD NOT to express an unwillingness in the past Everyone was angry because Sam wouldn’t turn off the television.

WOULD HAVE can refer to events in the past which did not actually happen I would have accepted the job, but I didn’t want to move house.

assumptions about the past Someone called after you left but didn’t leave a message. That would have been Cathy, probably.