may

may, might

1. With reference to present or future possibility, may and might are both used, but with may the possibility is more open and with might it is more tentative or remote: (may)

• The ACLU may have a strong case —Economist, 1980

• The cyclists may use up to 6,000 calories during a race —Times, 1983

(might) The news that the Met season might have to be cancelled…is an annual threat —Listener, 1980

• Some players get a ‘buzz’ from the game [of Space Invaders] and that might explain why they become addicted —Times, 1983

• What is a little surprising is that even the programme's adult representatives claim they don't quite know what a bonk might be —Today, 1986.

2. With reference to possibility in the past, may have leaves it open whether an event or circumstance was actually the case, whereas might have implies that it was not, and is explicit that it was not when the statement is part of an unfulfilled condition introduced by if or by inversion (as in the 1983 Daily Telegraph example below): (may have)

• It may have been an awful night…but the meat and potato pies were brill —Guardian, 1983

• Police say they're anxious to trace a car and a van which may have been used by the gang —television news broadcast, 1993

• (might have) ‘You might have been killed yourself.’ ‘Not much chance; the raid had already gone past us.’ —A. Crawley, 1983

• Had the Liberal Yellow Book been published in 1920 our history might have been different —Daily Telegraph, 1983

• Once he might have answered differently —might have said that the two things were different in kind —but now he was not so certain —D. Wingrove, 1990.

It is incorrect to use may have when the possibility it expresses is not an open one, although this misuse is becoming increasingly and disturbingly common:

• If some of the resources squandered this morning had been used more wisely, we may have been able to take steps to save his life —Scotsman, 1989

• This advice may have stopped a fashion faux pas.…‘I wore my favourite hound's-tooth miniskirt on my first day.…What a mistake’ —Times, 2004

• If Apple had licensed Windows for its computers instead of insisting on its own operating system, it may not have squandered the lead built up with the launch of the Macintosh in 1984 —Independent, 2006.

3. There are a few idiomatic uses of might and might have that are worth noting: You might have said something! (= you should have said something) / Might I suggest…? (= a polite, now somewhat old-fashioned alternative for May I…?). Might have is occasionally used with future reference, again with a suggestion of doubt about fulfilment:

• The wind has dropped so it feels hotter and tomorrow might be a degree or two higher —Sunday Mirror, 2007.