Page 51 - Advanced English Grammar in Use

M a y , m i g h t , c a n a n d c o u l d : p o s s i b i l i t y ( 2 )

Д Compare these sentences:
• I'll write the date of the meeting in my diary, otherwise I may/might/could forget it.
(= talking about present or future possibility)
• Jenny's late. She may/might/could have forgotten about the meeting. (= talking about past
possibility)
We use may/might/could (not 'can') + have + past participle to say it is possible that something
happened in the past:
л • I thought I saw Tom in town, but I may/might could have been wrong.
• • 'Where's Barbara's camera?' 'She may/might/could have taken it with her.'

We use might/could (not 'may' or 'can') + have + past participle to say that something was
possible in the past, but we know that it did not in fact happen:
• If I hadn't come along at that moment, Jim might/could have been the one arrested instead
of the real thief.
• The plan might/could easily have gone wrong, but in fact it was a great success.
We use might (not 'may') + infinitive to talk about what was typically the case in the past:
• During the war, the police might arrest you for criticising the king.
• Years ago children might be sent down mines at the age of six. (passive form)
We can also use could + infinitive in examples like this to talk about past ability (see Unit 22). For
example, 'During the war, the police could arrest you...' means that the police were legally able to
arrest you.
D We use may/might (not 'can') + have + past participle to say that by some time in the future, it is
possible that something will have happened:
• By next Friday I may/might have completed the report.
• His maths may/might have improved by the time the exam comes round.
We use may/might (not 'can') + be + -ing to say it is possible that something is happening now or
to talk about a possible future arrangement:
• Malcolm isn't in his office. He may/might be working at home today.
• When I go to Vienna I may/might be staying with Richard, but I'm not sure yet.
Could can be used in the same patterns instead of may or might, particularly when we want to
show that we are unsure about the possibility.
Notice that we can combine these two patterns to talk about possible situations or activities that
went on over a period of time until now (see also Unit 8):
• David didn't know where the ball was, but he thought his sister might have been playing
with it. (= from a past time until now)

О We use may/might/could + well/conceivably/possibly + have + past participle (compare Unit
20D) to say it is likely that something would have happened in the past if circumstances had been
different, or to say that by some time in the future it is likely that something will have happened.
(Notice that we don't use 'can well (etc.) + have + past participle'):
• I may/might/could conceivably have been tempted to take the job if it had been nearer
home, (passive form)
• By this time next week, I may/might/could well have left for Washington.

May, might, can, could: possibility (1) = Can and could: ability: