The words 一瞬{いっしゅん}, 瞬間{しゅんかん} and 一瞬間{いっしゅんかん} all seem to mean "instant", "moment". Is there any difference between them?

  • It seems I have to wait 23 hours to award the bounty!
    – Pedro A
    May 7, 2017 at 22:52

1 Answer 1


一瞬{いっしゅん} and 瞬間{しゅんかん} are natural Japanese words, but we don't usually use 一瞬間{いっしゅんかん}.

As nouns

一瞬 and 瞬間 are nouns.

瞬間 can be used to make a compound word, such as 瞬間{しゅんかん}湯沸{ゆわか}し器{き} (which means instant water heater, i.e., tankless water heater), while 一瞬 can not.

As adverbs

一瞬 can also be an adverb, which is used like:

  • 一瞬{いっしゅん}、彼{かれ}は立{た}ち止{どま}った。
  • 彼{かれ}は一瞬{いっしゅん}立{た}ち止{どま}った。
  • (He stopped walking and stood still for a short time.)

But you can't say:

  • 瞬間{しゅんかん}、彼{かれ}は立{た}ち止{どま}った。
  • 彼{かれ}は瞬間{しゅんかん}立{た}ち止{どま}った。

Instead, 瞬間 can be an adverb with 「に」, which is used like:

  • 瞬間{しゅんかん}にお湯{ゆ}が沸{わ}く。
  • 瞬間{しゅんかん}にお湯{ゆ}が沸騰{ふっとう}する。
  • (The water boils after a very short time.)

The following illustration depicts the difference between 瞬間に and 一瞬:

difference between 瞬間{しゅんかん}に and 一瞬{いっしゅん}

Therefore, you can also say 「一瞬{いっしゅん}お湯{ゆ}が沸{わ}く」, but it has a different meaning: the water boils for a brief specific duration, not before, not after. That is, the act of boiling lasts a short time.

Edit to address comments:

Why 「瞬間に、彼は立ち止まった」 or 「彼は、瞬間に立ち止った」 could not be said? Consider the following sentences, all using the adverb 「瞬間に」 which means "in a short time":

  1. 彼{かれ}は瞬間{しゅんかん}に立{た}ち止{どま}った。
  2. 彼{かれ}は瞬間{しゅんかん}に立{た}ち上{あ}がった。
  3. 鳥{とり}たちは瞬間{しゅんかん}に飛{と}び去{さ}った。
  4. 猫{ねこ}はびっくりして瞬間{しゅんかん}に飛{と}び上{あ}がった。
  5. 鳥{とり}たちは物音{ものおと}にびっくりして瞬間{しゅんかん}に飛{と}び去{さ}った。

They seem grammatically correct, but only the first one does not sound natural as Japanese. Why does this happen? I could not get the exact answer at hand, but I conjectured the answer as follows:

Generally, it is difficult for a moving object to stop suddenly without any residual movement because of an inertial force. If I am allowed to use the term in the illustration, I could say that if the state A describes something moving and the state B describes the state of standstill of the same thing, the transition to the state B in a very short time is difficult, therefore the sentence does not sound natural.

On the other hand, the other four sentences express a sudden shift to a state with movement, and I think that therefore they sound natural. You can easily judge whether a certain thing is moving or not, so the state of standstill is more strictly judged than the state of movement.

I found it interesting that the logical understanding of physics affects a Japanese sentence.

Evidence for logical Japanese sentences

As I said the sentence 1 does not sound natural, because it is not scientifically logical. But you could make the sentence 1 natural by adding an appropriate phrase to it like "no way", "he told a lie", "it's impossible" "to my astonishment", "with some fluctuations" "almost/nearly", etc. which make the meaning of the whole sentence logical. Then, the following sentences including the sentence 1 sound natural as Japanese.

  1. 彼{かれ}は瞬間{しゅんかん}に立{た}ち止{ど}まったと言{い}ったがそんなの嘘{うそ}だよね
  2. びっくりしたなぁ、 彼{かれ}は瞬間{しゅんかん}に立{た}ち止{ど}まった
  3. 少{すこ}しよろけたが彼{かれ}はほぼ瞬間{しゅんかん}に立{た}ち止{ど}まった


  • Thank you. I am still a bit confused. From what you've said, it seems that 一瞬 and 瞬間に are both adverbs but still not interchangeable, right? Could I say "彼は瞬間に立ち止った"? If yes, would the meaning be different from "彼は一瞬立ち止った"? Also, does "彼は一瞬立ち止った" imply that "shortly after, he started walking again"?
    – Pedro A
    May 1, 2017 at 14:30
  • @Hamsteriffic >still not interchangeable, right? Right. >Could I say "彼は瞬間に立ち止った"? No. "彼は瞬間に立ち止った"? does not make sense. >does "彼は一瞬立ち止った" imply that "shortly after, he started walking again"? May be yes, but not aboslutely. Because he could crouch there.
    – user20624
    May 1, 2017 at 14:53
  • Your phrase "The water boils at some moment, never before nor after" refers to "瞬間にお湯が沸く" or "一瞬お湯が沸く"?
    – Pedro A
    May 1, 2017 at 15:17
  • Hamsteriffic It refers to "一瞬お湯が沸く". Though the phrase is scientifically questionable but grammatically correcrt. We say "一瞬顔{かお}が曇{くも}る", "一瞬笑{え}みがこぼれる".
    – user20624
    May 1, 2017 at 15:43
  • Thanks... Unfortunately I'm still confused... I was hoping you would say it refers to "瞬間にお湯が沸く"... With the first part of your answer, it seemed to me that 瞬間 is more like a specific point in time, such as "最後の瞬間" while "一瞬" is more like a brief period of time (so the first is a point, the other a duration); but your examples about water boiling seem to reverse this idea. Can you edit your answer with more examples in which both "一瞬" and "瞬間に" can be used and resulting in different meanings?
    – Pedro A
    May 1, 2017 at 15:54

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