MODAL VERBS

Must / Mustn’t

a) Must expresses

  1. obligation or command.

You must do your homework.

Traffic must keep to the left in England.

  1. deduction or logical conclusion

If she left home an hour ago, she must arrive soon.

·  In this case the usual negative is cannot / can’t.

If she doesn’t speak English, she cannot / can’t be a good student.

b) Mustn’t (must not) is used

  1. to express a negative obligation

You mustn’t miss that film.

  1. to express a prohibition

Cars must not park here.

  1. to give advice

You mustn’t do that

Note: The negative of must is needn’t (need not) when the meaning is “it is not necessary”, “there is no obligation”

Must I go home? No, you needn’t.

Ought to

Ought to is used

  1. to express duty or moral obligation

He ought to pay for the meals.

You ought to obey your parents.

  1. to give advice

You really ought to look for another job.

(Ought to can often be replaced by should, but the former is more emphatic.)

Could

Could can be used

  1. as the past of can, expressing power, ability or capacity.

He could make me that table.

She could see very well.

  1. in indirect speech.

He said he could speak German.

  1. to express permission.

Mum said we could go to the cinema.

  1. in polite requests

Could you lend me some money?

  1. to express possibility

If he knew about it, he could travel by bus.

  1. suggestion.

You could always try and cook.

Shall / Should

a) Shall is used to express

  1. futurity (Shall +infinitive +1st person)

I shall (=I’ll) be 18 next month.

  1. an offer.

Shall I answer the phone?

  1. the speaker’s will: command, promise, threat.

You shall have the cheque next week.

  1. a suggestion

Shall we dance?

  1. intention on the part of the speaker.

We shall let you know our decision.

b) Should

  1. is the past tense of shall. It can indicate future in the past.

I said that I should write.

  1. is used to form the conditional.

I should get the job if I worked harder.

  1. can express moral obligation or desirability.

I think you should apologise.

He should have been more careful.

  1. is used in instructions and corrections when must sounds too peremptory.

Applications should arrive by May 10th.

Will / Would

a) Will is used to express

  1. futurity (Will +infinitive +2nd and 3rd persons)

He will fly tomorrow.

  1. a request

Will you come in?

  1. an offer

Will you have a cup of tea?

  1. an order

Nobody will leave the room until the police arrive.

  1. willingness, promise or determination

I will pay you at your price.

I will send you a postcard.

We will make the computer work.

b) Would

  1. is the past tense of will. It can indicate future in the past.

She said that she would leave.

  1. is used to form the conditional.

If they had the money, they would buy the car.

  1. may indicate habitual actions in the past.

He would get up at 8 o’clock when he was a child.

  1. may be used as the past

I don’t know. She wouldn’t say. (didn’t (want to) say)

Can / Can’t

a) Can is used to express

  1. power, ability or capacity.

She can make her own dresses.

They can speak English fluently.

He can swim.

  1. possibility.

Can I wash it by hand?

  1. permission.

You can go to the party.

b) Can’t (=cannot) is used to express

  1. prohibition.

You can’t smoke here.

  1. impossibility.

It cannot be a real diamond.

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