Utilisation de verbes modaux

We can use these modal verbs (also called modals of deduction, speculation or certainty) when we want to make a guess about something. We choose the verb depending on how sure we are.

1: Talking about the present:

must / might / could / may / can't

must + infinitive

might / might not + infinitive

could / could not + infinitive

may / may not + infinitive

can't + infinitive

For example:

I am waiting for Julie with another friend, David.

I ask: 'Where is Julie?'

David guesses:

She must be on the bus. (I'm fairly sure this is a good guess)

She might come soon. (maybe)

She could be lost. (maybe)

She may be in the wrong room. (maybe)

She can't be at home. (I'm fairly sure this isn't true)

Notice that the opposite of 'must' is 'can't in this case.

Will / won't

We use will and won't when we are very sure:

She'll be at work now.

Should / shouldn't

Should and shouldn't are used to make an assumption about what is probably true, if everything is as we expect:

They should be there by now.

It shouldn't take long to drive here.

This use of should isn't usually used for negative events. Instead, it's a better idea to use will:

The underground will be very busy now (not: 'should be').

Can

Can is used for something that is generally possible, something we know sometimes happens:

Prices can be high in London.

Can is not used to talk about specific possibilities:

He could be on the bus (not: 'can be').

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