Modal verbs

simple Modal verbs

let's go

main features of modal verbs

They are always followed by a verb in the infinitive form

They express something: obligation, prohibition, ability, possibility...

Most of them aren't followed by preposition 'to'

Most of them don't need the third person singular -s

CAN

ability

request, permission

possibility

She can take the bus to work

She can speak Chinese

Can I use your laptop?

be able to

It can be used as a synonym of "can" This is the exception: it must be conjugated and is followed by preposition 'to'

ability

possibility

Will you be able to arrive on time?

She is able to speak Chinese

CAN't

inability

prohibition

disbelief, deduction

Students can't use the mobile phone in the highschool

He can't be wealthy. He lives in a slum

I can't speak German

could

past ability

polite request

posibility

He could exercise for hours when he was young

Could you please open the door?

You could come to the party with Paul

may / might (NOT)

They are synonyms, so both can be used

posibility (when we aren't sure)

may is also used as polite request

I might / may travel to the United States next summer

May I have some coffee, please?

should / ought to shouldn't / ought no to

advice / opinion

You should give up smoking... / You ought to give up smoking You shouldn't smoke / You ought not to smoke

need to

necessity / obligation

They need to find an outfit for the special day

have to

necessity / obligation

This beighborhood is not safe. You have to relocate as soon as possible

don't have to don't need to needn't

lack of obligation / necessity

You don't have to work tomorrow. It's Sunday! You don't need to work tomorrow. It's Sunday! You needn't work tomorrow. It's Sunday!

must

Logical conclussion

necessity / obligation

The athlete has won many medals. He must train hard

You must study if you want to get good results

mustn't

prohibition

People mustn't draw graffiti on public buildings

would

formal request

offer

Would you like to help me with my homework?

Would you stop cutting into the conversation?

perfect Modal verbs

let's go

main features of perfect modals

They are used to talk about the past: situations that have already happened

They express something: logical conclusion, guess, certainty, criticism...

They follow the structure: modal + have + past participle form of the verb

could have

The ability to do something in the past, but which in the end was not done

You could have avoided that accident.

should have

criticism or regret after an event (positive form)

We should have left earlier. There's a traffic jam now and we won't arrive on time.

shouldn't have

criticism or regret after an event (negative form)

You shouldn't have drunk so much. Now you've got a hangover.

would have

desire to do someting which wasn't actually done due to external circumstances

I would have met you yesterday, but I couldn't leave the house because of the storm.

needn't have

to expressthat there was no obligation or necessity to do something

You needn't have bought me flowers! That's very kind of you.

must have

a certainty or logical conclusion about an event in the past

He must have felt exhausted after that long trek.

might / may have

a guess about something which happened in the past

She's not here. She might / may have turned down the invitation.

can't / couldn't have

certainty that something didn't happen

He can't / couldn't have designed that skyscraper. He's not an architect.