I'm having a hard time understanding how と works with negative verbs. With positive verbs, it is easy to see the timeframe of いい because it occurs after the verb happens, but if the verb ends in ない, how do I know when いい happens when a verb ending in ない means nothing occurs? I only seem to have this problem with いい and not だめ. For example, 食べないとダメ means that if you don't eat, you will eventually have something bad to happen. If reworded as 食べないとだめになる, the sentence still makes sense because the original sentence also reflected a change in state. However, in a sentence like 電池が爆発しないといい, 爆発しないとよくなる seems to have a different meaning.

  • Especially with your 爆発-example I get the feeling しないとよくなる wouldn't be used, except some very distinct cases. I feel, that maybe a example with a more process-like verb could be better, for example 治るといいん/治るとよくなる. Which could be "I hope (you) get better" (word by word "If you get better, its good.") / "If you get better, it gets better."
    – dinogeist
    Mar 11, 2015 at 4:22
  • 2
    I'm not really sure what you are stuck with but at least 食べないとダメ never means that way. It's a simple prohibition of not eating and there is no timeframe or anything. Also 食べないとだめになる / 爆発しないとよくなる sounds very unnatural if not ungrammatical. Do you want to mean "it will eventually get better if the battery doesn't explode"? Then something like 電池が爆発しなければいずれよくなるだろう would do but いずれ "eventually" seems important here.
    – isayamag
    Mar 11, 2015 at 5:46
  • I feel like ダメ reflects a change in state. If you spend some time in 食べない you will enter the state of ダメ. If it was just a general prohibition of not eating, then it should be something like 食べないことはダメ, which is different from 食べないとダメ. I'm mainly wondering why 食べないとだめになる makes sense even if it feels unnatural yet 爆発しないとよくなる does not make sense, which I feel is because I don't fully understand what 爆発しないといい is. I guess it's something like does 爆発しないといい reflect a change of state like 食べないとダメ does?
    – Joe
    Mar 11, 2015 at 5:58
  • Mmm...As a native Japanese speaker, I have never heard of 食べないことはダメ thing and again, I have to say definitely 食べないとダメ contains no connotation of your "change in state". Plus, I don't think 食べないとだめになる makes sense. Of course 爆発しないとよくなる doesn't either.
    – isayamag
    Mar 11, 2015 at 6:32
  • I know that 食べないことはダメ is pretty much never said, but if it was said, what would its meaning be? Would it be equivalent to 食べないとダメ? In addition, in 食べないとダメ, what does ダメ modify as an adjective?
    – Joe
    Mar 11, 2015 at 6:46

2 Answers 2


First of all, "食べないとダメ" means "you have to eat," not meaning "食べないとだめになる."

In this topic's context, "いい" is used when you describe your hope or wish. For example, "爆発しないといいな" means "I hope it won't explode."

  • "You have to eat" is a localization of 食べないとダメ, it's not the precise definition. As far as I can see, there is no difference from 食べないとだめになる since they both have the literal meaning of "If you don't eat, there will be something bad." I know that the general idea of 爆発しないといい would be "I hope it doesn't explode" but that's not what it literally means.
    – Joe
    Mar 11, 2015 at 5:12
  • What I don't get is this part: "they both have the literal meaning of "If you don't eat, there will be something bad."" I think "食べないとダメ" doesn't literally mean "食べないとだめになる", but instead it just means "食べなければいけない." What "ダメ" means in this context is just obligation/duty, not "a change of state." The way you think when you see the word "だめ" seems weird. Why don't you just remember "~しないとだめ" means just obligation?
    – Kei
    Mar 11, 2015 at 18:25
  • I don't see where you got ダメ's definition as obligation/duty. You also write 食べなければいけない as 食べなければいけなくなる and it would still be understandable. Anyway, a better example to illustrate my point would be why I can write 爆発しないとうれしい and 爆発しないとうれしくなる and yet 爆発しないとよくなる does not work.
    – Joe
    Mar 11, 2015 at 19:13
  • The reason why "爆発しないとよくなる" doesn't work is "誰がよくなるのか分からないから(you don't know who's gonna get better)," while the other two are referring to "私." By the way, "爆発しないとうれしい" may be grammartically correct but I can't see where to use this phrase. Like "I'd be happy if the nuclear power plant won't explode?" On the other hand, "爆発しないとうれしくなる" sounds even worse. It may grammartically work, but at least, as a Japanese, I've never heard or used this phrase in my entire life. As for your first remark in the previous comment, what I meant was that the definition of "~しないとだめ" is obligation/duty.
    – Kei
    Mar 11, 2015 at 20:07
  • I think the problem is that I am misunderstanding how と works, specifically on when the part of the sentence after と occurs. Is there a difference between エアコンをつけないと暑い and エアコンをつけないと暑くなる? Is the first sentence saying that it is hot if you don't turn on the air conditioning or that it will be hot if you don't turn on the air conditioning?
    – Joe
    Mar 11, 2015 at 23:47

yes, the sense is different:

-爆発しないといい you express your hope, you hope that it won't happen

-爆発しないとよくなる doesn't make much sense with this verb, but you simply state that something good will come out of not doing an action. There is no notion of hope

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