In American English, are "mightn't have" and "might not have" both often used in speaking and writing?

How about "couldn't have" and "could not have"?

How about in British English? Thanks!

  • 1
    I'm sure I've heard it sometimes. We even have mightn't've. :-) Mar 24, 2014 at 0:42
  • 1
    I'd say "mightn't have" is the one I hear or see least regularly (in the US), but any of these would be understood. Mar 24, 2014 at 0:43
  • @DamkerngT.: Which dialect of English or region do you refer to?
    – Tim
    Mar 24, 2014 at 0:48
  • @Tim I'm not sure because I listen to both accents (AmE and BrE) a lot. Earlier I was more used to AmE, but I found myself listen to BBC Radio more and more lately. Maybe I've heard it in both accents. Mar 24, 2014 at 1:01
  • 2
    @DamkerngT. Pronounced /maɪʔənʌv/ where I come from. Mar 24, 2014 at 2:08

2 Answers 2


My gut feel is that the mightn't contraction is more common in BrE than AmE (but I've no reason to think most Americans find it at all "unusual").

I'm not sure if this is a valid way of using Google Books estimated results, but note these figures...

1: color:159M, colour:53M
2: might + color:12M, might + colour:6M
3: mightn't + color:4310, mightn't + colour:5680

According to #1, there are three times as many instances of US color as there are UK colour. Since there's no reason to suppose Americans use the word any more often than Brits, I assume the relevant US corpus is about three times bigger than the US one.

All things being equal, we could expect the #2 AmE count to be about 18M, not 12M. But note that overall prevalance of might has fallen by a third in the last couple of centuries. Older texts in the Google Books corpus are more likely to be BrE, so the AmE aversion to might is weaker than the bare figures suggest.

But after allowing for the implication of the above (Americans are perhaps 20-30% less likely than Brits to use the word might in any given utterance), we should still expect the #3 AmE count to be 11K, not 4K.

Regardless of whether the absolute values of those Google Books estimates are accurate, I see no reason to suppose that the ratios aren't meaningful. So I think this validates my gut feel.

The figures for couldn't + color:2.8M and couldn't + colour:0.85M suggest that the US aversion to mightn't doesn't extend to couldn't.

  • 3
    I'm in the U.S., and I'd concur with your last statement. I would have no qualms about writing couldn't in a letter (sorry I couldn't be at your wedding), but I think that – until today – I've never written the word mightn't (sorry, I mightn't be able to attend your anniversary party). That said, I'd have no problem understanding it, of course.
    – J.R.
    Mar 24, 2014 at 9:04
  • 1
    I'm from the U.S. and would say that "mightn't" is rather uncommon. Although I do note that Firefox's US English spellcheck does recognize it. Then again, I've seen it written much more often than spoken.
    – trlkly
    Aug 8, 2014 at 8:54

In American English mightn’t is extremely uncommon, but still understood.

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