Obligation
|
| Certainty (or near certainty) about now, the future or generally |
will, would, must, can, can't, could, couldn't |
There's someone at the door.
'That'll be the postman'.
'It can't be. He's already been.' |
| Certainty (or near certainty) about the past |
will have, won't have, would have, wouldn't have, must have, can't have, couldn't have |
'They won't have heard the news, will they?'
'They must have heard by now, surely.' |
| Probability about now, the future or generally |
should, shouldn't, ought to, oughtn't to, may/might well (not), could well, might easily |
'The weather should be good tomorrow, shouldn't it?'
'Actually, the forecast said it may well rain.' |
| Probability about the past |
should have, shouldn't have, ought to have, oughtn't to have, may/might well (not) have, might easily (not) have |
'Jan should have finished writing her article by now, shouldn't she?'
'She may well have done, but I haven't seen it yet.' |
| Possibility about now, the future or generally |
could, may (not), might, mightn't, may/might/could just |
I might (just) have time to get to the library before it closes. |
| Possibility about the real past |
could have, may (not) have, might have, mightn't have |
Jim might not have checked his e-mail yet. |
