can: possibility and probability

1 Possibility

We use canto say that situations and events are possible.

• Scotland can be very warm in September.


• 'Who can join the club?' 'Anybody who wants to.'


• There are three possibilities: we can go to the police, we can talk to a lawyer, or we can forget all about it.


• 'There's the doorbell.' 'Who can it be?' 'Well, it can't be your mother. She s in Edinburgh.

We use could to talk about past possibility.

It could be quite frightening if you were alone in our big old house.

2 Probability

We do not usually use can when we are talking about the chances that something is true, or that something will happen. For this idea (probability), we prefer could, mayor might.

• 'Where's Sarah?' 'She may/could be at Joes place.' (not 'She can be . . . ')


• We may go camping this summer. (not We can go . . . )

3 could have ...

We use a special structure to say that something was possible, but did not happen.

could have + past participle

• That was a bad place to go skiing — you could have broken your leg.
  


• Why did you throw the bottle out of the window? It could have hit somebody.