Modal Verbs

Modal Verbs

• Obligation/Necessity
• Absence of necessity
• Permission/Prohibition
• Possibility
• Ability/Inability
• Logical Assumptions/Deductions
• Criticism
• Offers/Suggestions
• Probability
• Advice

Obligation/Necessity

must - strong obligation to do sth., the speaker himself has decided that sth is necessity

I must contact the school for some information.

have to – strong necessity/obligation, when objective circumstances make us do sth

We have to wear uniform at school.

had to – past form of must and have to

should/ought to – duty or weak obligation

We should clear away the mess in the kitchen.

Absence of necessity

don’t have to-don’t need to-needn’t - sth which isn’t necessary to do in the present/future

You don’t have to dress formally today.

needn’t have V3 – sth which wasn’t necessary to do in the past but it was done

You needn’t have cooked so much food. We weren’t hungry.

didn’t have to – sth which wasn’t necessary to do. We don’t know if it was done or not.

He didn’t have to invite everyone to the party. (We don’t know if he invited everyone.)

Permission/Prohibition

can/may - used to ask for/give permission. May is more formal than can.

Can/May I use your phone, please? – Yes, you can/may.

mustn’t /can’t– forbidden to do sth, against the rules, not allowed to do sth.

You mustn’t/can’t park here.

Possibility

can + present infinitive - general/theoretical possibility

Going to the gym can be boring.

could/may/might + present infinitive - possibility in a specific situation.

She should take a map with her. She might get lost.

We can use can/could/might in questions, but NOT may.

How difficult can it be?

could/might/would + perfect infinitive sth in the past that was possible but didn’t happen

He could have come with us, if he hadn’t missed the train.

Ability/Inability

can - ability in the present/future.

I can speak Italian fluently.

could – general or repeated ability in the past

I could sing quite well when I was younger.

was(n’t) able to – (in)ability on a specific occasion in the past

I was able to (wasn’t able to) find all the answers.

couldn’t – any kind of inability in the past

I couldn’t read or write when I was four.

Logical Assumptions/Deductions

must = almost certain that it is/was true

He isn’t at work. So he must be on his way home.

may/might/could = possible that it is/was true

The computer is out of order. It may be broken.

can’t/couldn’t = almost certain that it is/was impossible

That can’t be John! John has blue eyes and blond hair.

Criticism

could

You could at least be polite to her. (present)

You could at least have called to cancel it . (past)

should

You should call them back. (present)

She should have told us. (past)

Offers/Suggestions

would

Would you like a cup of tea?

shall

Shall I give you a lift?

can/could

We can/could watch TV.

Can I give you a lift?

Probability

will

He will call me tonight. (100% certain)

should/ought to

The weather should/ought to get better tomorrow. (90% certain, future only)

Advice

should/ought to - general advice

You should stop smoking.

shall – asking for advice

Shall I enter the competition?