I learnt that the negative form of い-adjective is: remove the trailing い, then add くない. Example: 赤い→赤くない

However, I've been watching Japanese livestream and following her twitter. Sometimes, she omit the く in negative form of い-adjective. Example: from her Twitter post


In her livestream, she also sometimes said やばない instead of やばくない, and 酷ない instead of 酷くない.

That makes me wonder if this is somewhat common in Japan (perhaps dialect?), or just her habit. If it matters, she's from Kumamoto.

  • 1
    Here in Kyoto we daily say [おいしない]{LLHLH}, [あかない]{LHLH} etc. to mean おいしくない, あかくない. Some (older?) people tend to pronounce them おいしない, あかない etc., though.
    – chocolate
    Commented Apr 29, 2017 at 13:40

3 Answers 3


There are at least three types of omission of く, which should be distinguished.

The "traditional western" euphoric change is called ウ音便 and is described in this question, this one and a chart in this page. ku becomes (y)u, etc. This sounds old-fashioned and elegant. While this is commonly heard in samurai dramas, only a few courteous elder people use this today.

  • おいしくない → おいしゅうない
  • くるしくない → くるしゅうない

In the (modern) Kansai dialect, instead of saying ku, the vowel right before k will be elongated:

  • おいしくない → おいしいない
  • くるしくない → くるしいない
  • あつくない → あつうない
  • からくない → からあない
  • くろくない → くろうない (kurônai)

The "recent slangy" version is different from these. This pattern is typically found on Twitter and such and look like this:

  • おいしくない? → おいしない?
  • やばくない? → やばない?
  • ひどくない? → ひどない?

It's similar to the Kansai dialect, but no elongated vowel is employed. And I doubt this pattern is dialectal; I often see young people living in Kanto say things like these. I believe this is a very new phenomenon (it suddenly emerged in the last 5 years or so) among young people, and AFAIK this is mainly used as a question sentence: "Isn't it ~~?" I am in my thirties and I'm perhaps already too old to use this naturally :D

As for 美味しない in the tweet in question, the user is not a Kansai dialect speaker. So it's not archaic elegant 美味しゅうない, nor typical Kansai 美味しいない, but recent slangy 美味しない. I think most young people who say these are doing so more or less playfully, knowing it's not standard. For now I don't think this will be part of the formal Japanese grammar in the future.


"やばない?" instead of "やばくない?" is kind of slang (of slang) which some young people use. But I don't often see this omitting "く" with other adjectives. The example "キャベツ美味しない。" doesn't make sense to me, so I think it's her mistake or just her habit.

  • 4
    For me the く-omission in "キャベツ美味しない" works as well (and probably in the same way) as in "やばない?" In fact く is omissible with all adjectives I've tried in my head so far (though the く-less form feels more informal.) It's more likely dialectal than idiolectal or erroneous.
    – goldbrick
    Commented Apr 28, 2017 at 11:45
  • Any idea which dialect(s) might do this @goldbrick? Commented Apr 28, 2017 at 12:36
  • 2
    The bag of wisdoms holds that "く抜き言葉" is Kansai-dialect, although the inquirer, a Kyotoite, says they never use it. (All the three answers there point out ウ音便化 is part of the process.) This blog post also says it's a Kansai thing. And I can back it up too, at least partially, since I grew up in Osaka.
    – goldbrick
    Commented Apr 28, 2017 at 14:02
  • Couldn't find any material linking it to Kumamoto though. Maybe she picked it up while living somewhere in Kansai? @leoboiko
    – goldbrick
    Commented Apr 28, 2017 at 14:02
  • "く抜き言葉" must be inspired by ら抜き言葉 but not be as widely used because I found something completely different when googling video examples of "関西弁"+"く抜き"...
    – siikamiika
    Commented Apr 28, 2017 at 15:20

赤{あか}くない ー 赤{あか}ない ー not red
美味{おい}しくない ー 美味{おい}しない ー not delicious

I often heard like the sound in Kansai.

They don't pronounce them as "aka-nai" and "oishi-nai", but pronounce them like "aka-a-nai" and "oishi-i-nai" or "aka:nai" and "oishi:nai".

where ":" means to sound the vowel long

As the samples show, they pronounce them by omitting "く" and adding the same vowel or sounding the vowel long just before the く in the formal forms.

  • 1
    Hmm, the way I've often heard it and the way I would say it, く is just dropped and no vowel lengthening is added in its place, though I think I've heard it the other way often enough.
    – goldbrick
    Commented Apr 28, 2017 at 17:27
  • goldbrick Think about the difference between 赤ない and 開かない, you'll find the subtle difference. 赤ない has some traces just after "赤aka" such as enlonging the vowel, placing a pose or placing a further stress, etc.
    – user20624
    Commented Apr 29, 2017 at 10:27

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