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I've just learned that `～わけにはいけない` as in `断{ことわ}るわけにはいけない` ("I can't refuse")
apparently isn't valid but `～わけにはいかない` is, even though I've been using the
former frequently.

But what is the difference between `いかない` and `いけない` and when should they each
be used? Also, is `(te form)はいかない` valid? I'm guessing `～してはいかない` isn't valid
but `～してはいけない` is.

Is `うまくいけない` or `納得いけない` valid? In English I think "this can't go well" or "I
can't tolerate that" sounds like it would work, but I'm not sure it would in
Japanese.
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2011-11-21T00:32:46.633
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2011-12-29T05:20:11.040
2011-12-29T05:20:11.040
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question
grammar expressions
What's the difference between 「いけない」 and 「いかない」?
`いかない` is less often a problem as it's derived from `行く`, but `いけない` can be
both the negative potential form of the verb `行く` "to go" and the negative
form of the verb `行ける` "to be good (at)/to go well/to be acceptable." 6

Therefore `いかない` and `いけない` may appear to be similar, but they can actually be
totally different.

* * *

`いかない` "won't go/doesn't go" from `行く`:

> **～わけにはいかない** : An expression which means "I cannot very well" when after a
> verb that isn't in the past tense. 5
>
>   * `いつまでもけんかしているわけにはいかない` "I can't very well keep fighting forever." 7
>

`いけない` "unable to go/can't go" from `行く`:

> **そのパーティーにいけない** : Can mean "I can't go to the party." 2

`いけない` "unacceptable/bad" from `行ける` 5:

> **～てはいけない** : Can mean "unacceptable if" however it's more often translated
> as "must not/may not." Means "must/have to" if on the end of a negative
> verb. 5
>
>   * `走{はし}ってはいけない` "you must not run."
>   * `走らなくてはいけない` "you must run."  
>  
>
>

>
> **～はいけない** : Can mean "won't do/no good/bad" as well as "naughty."
>
>   * `彼{かれ}はいけない` "he is naughty." 1
>   * `それはいけない` "that's bad" in many contexts. 2  
>  
>
>

>
> **～て（で）いけない** : Means "undesirable/unpleasant" after a conjunctive form.
>
>   * `いい人だが、おしゃべりでいけない` "A great person, but his/her chattering isn't to be
> desired." 4  
>  
>
>

>
> **～といけないから… or ～といけないので… etc** : On the end of verbs means "it will be bad
> if ~ happens so ..."
>
>   * `雨{あめ}が降{ふ}るといけないから傘{かさ}を持{も}ちなさい` "It will be bad if it rains so take
> an umbrella." 1  
>  
>
>

>
> **"It's your fault that"** :
>
>   * `お前がよく[注意]{ちゅうい}していなかったのがいけないんだ` "It was your fault that you weren't
> careful." 3  
>  
>
>

>
> **"Hopeless"** : (`駄目{だめ}`) if used as `もういけない` or `やっぱりいけなかった`.
>
>   * `あの病人{びょうにん}はもういけないようです` "It seems that patient is beyond hope." 1
>   * `試験{しけん}はやっぱりいけなかった` "Just as I feared, I've failed the exam." 1  
>  
>
>

>
> **"Unfortunate/too bad"** (expressing sympathy):
>
>   * `それはいけません` in response to hearing that someone is unwell would mean
> "it's unfortunate that you are unwell." 1  
>  
>
>

>
> **Other meanings:**
>
>   * "Beyond hope of recovery" if used as `いけなくなった` 3
>   * "Unable to drink alcohol" as in `あまりいけない口でして` 4
>   * "Darn!" when by itself, similar to `しまった` or `ちくしょう` 1
>   * Used by females as in `あ、いけない、どうしよう` "Oh dear, now what am I going to
> do?" 1
>

* * *

**Sources:**

  1. Louis' provided images
  2. [the lang-8 link as above](http://lang-8.com/315974/journals/1188521/%25E4%25BE%258B%25E6%2596%2587%25E3%2581%25AE%25E8%25B3%25AA%25E5%2595%258F)
  3. [Daijirin](http://dic.yahoo.co.jp/dsearch?enc=UTF-8&p=%E3%81%84%E3%81%91%E3%81%AA%E3%81%84&dtype=0&dname=0ss&stype=0)
  4. [Daijisen](http://dic.yahoo.co.jp/dsearch?enc=UTF-8&p=%E3%81%84%E3%81%91%E3%81%AA%E3%81%84&dtype=0&dname=0na&stype=0&pagenum=1&index=00805400)
  5. [Kodansha's furigana Japanese dictionary](http://rads.stackoverflow.com/amzn/click/4770024800)
  6. [JMDict](http://www.csse.monash.edu.au/~jwb/jmdict.html)
  7. [Space ALC](http://www.alc.co.jp/index.html)
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2011-11-26T07:01:55.410
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2011-12-02T08:05:43.347
2011-12-02T08:05:43.347
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answer