Why would you want to?Here's part of the book Focus on Grammar 5:
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Can't we use "couldn't" to talk about future possibility?
I don't see anything about the future thereWhy would you want to?
But, now I think of it, it would make sense in a case like this:
'I couldn't start at 8.00 because they had sent the wrong paper. It was gone 9.30 when the courier arrived with the right one.'
Can we use "couldn't" to talk about future possibility?
Doh! [Note to self: read the question.]I don't see anything about the future there
They all have the same meaning, but may is more formal than might and could.I might see you tomorrow if you're in the office.
There may be another issue that we don't know about.
This illness could be prevented.
I'll try the pharmacy, but it might well be closed now.
She may well have to rethink her plan.
That could well be true.
Couldn't is different from may not and might not. It means something is impossible.We may not need waterproof jackets, but I'll pack them anyway.
Safi might not come today as he has his driving test.
This illness could be prevented.
These are not very good examples of could being used for future possibility.That could well be true.
What could happen?It could happen.
It depends on the subject. It's using "could" to talk about the future. Somebody says, "What about XYZ?" Then I say, "It could happen." (It's a possibility.)What could happen?
In some old books, and in the speech of a dwindling number of old people, you may also (in BE) come across "mayn't".
The negative forms are may not and might not (or mightn't).