Both 間 {あいだ} and 内 {うち} can be used to describe time span relative to specific situations, similar to "while" in English. But are they interchangeable all the time? Are there any scenarios where one can use one of them but not the other? Are there differences in nuances?

Example sentences of my own (I'm not sure if they are correct or not so if they sound wrong please point out why):




Edited to replace the word "measure" with a better concept.

refers to the time space between two points; speaker feels he has the ability to determine a start and end point at the moment of making the statement. (間 has explicit time boundary)

however refers to "time space within"; for when it is difficult for the speaker to determine a start and end point. It refers to the general time during which an event/state is occuring. (No explicit time boundary for 内)

That is why it seems strange to say (though not totally unacceptable)[1]:


But is okay to say:


Because one cannot assess the start and end point of the duration within "not rain"

In your example 先生が見てない(間に/内に)逃げよう, the time during "teacher is not looking" isn't a predictable or planned event (No explicit time boundary). Therefore 内に would be more appropriate for your example sentence.

Edited: To try to explain the apparent contradiction with Tsuyoshi's example using 晴れている:




It should have something to do with the speaker's expectation of future circumstances:

The speaker takes the default standpoint of "clear weather" as a default weather.

We normally do not worry "when the duration of [clear weather] ends". But rather we would think in the manner of "when does [other weather] begin?". It becomes unimportant to assess a start and end point for a default standpoint. Since it's a default standpoint, both 間 and 内 can be used and will not sound unnatural or not smooth.

For [other weather] there is a start and end point, but the speaker expects [other weather] (e.g. rainy) to behave in a way that he cannot determine a start and end point for it.

Now for the case of "teacher is not looking", the speaker takes the default standpoint of "teacher is always paying attention" because that is how he would expect the teacher to behave. The alternative: duration of "teacher is not looking" becomes hard for the speaker to determine a start and end point.


  • [1] Makino, S., & Tsutsui, M. (2010). A dictionary of basic Japanese grammar. pg. 512-515 entry for uchi ni
  • Suppose if it was "先生が見てなかった___逃げました", then can we say it is now measurable (since it was in the past so there was a time boundary the "sensei not looking" situation ended) and hence we can use 間? – Lukman Aug 12 '11 at 12:47
  • I don't think so. The duration of the "teacher looking" has an indeterminate start and end time, regardless of completion of action. That is to say even after he looked, you cannot suddenly have the information of exactly when he started, and how long he did it for. – Flaw Aug 12 '11 at 16:10
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    I cannot understand what you mean by “measure.” I think that it is possible to measure the time of not raining in the same way to measuring the time of raining. – Tsuyoshi Ito Aug 12 '11 at 16:14
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    Perhaps "measure" is not a good word to describe what i'm thinking. It should be the "speaker's ability to determine a start and end point at the moment of making the statement". Things like "duration of vacation" - one can assess the start and end. But for "duration while it's not raining" or "duration of a person's gaze", it's difficult to put a starting and ending point. – Flaw Aug 12 '11 at 16:22
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    Thanks, now I see what you mean. But unfortunately I cannot agree. From the page which Axioplase linked, 晴れている間に作業を終わらせよう is a correct sentence (which I agree), which seems to be a counterexample. – Tsuyoshi Ito Aug 12 '11 at 16:50

In the example you give and similar constructions, I think they are pretty much interchangeable.

I however found some interesting Q&A on a bbs:

  • 若い[×間に][○うちに]いろいろなことを経験したい。
  • 忘れない[×間に][○うちに]メモしておこう。
  • 全部見終わらない[×間に][○うちに]出て行ってしまった。
  • つきあっている[○間に][○うちに]好きになってきた。

The conclusion of this link is 間 is a span of time between two points, 内 is the "inside" of a "time frontier". 内 seems thus used with a change of state (with the frontier distinguishing the two states), until that change happens.

Chie suggests a chance in 内 that isn't implied in 間。

  • 子供が寝ているうちに電話する (now or never!)
  • 東京に旅行しているうちにいろんなところへショッピングに行く (I may not be able to do that much shopping before a while!)

Hope that helps!

  • What do you think about Flaw's statement about the measurability of the time space as a requirement to use 間? – Lukman Aug 12 '11 at 12:44

I do not fully understand the difference between 間に and うちに and the following is based on my impression, but let me write it in the hope that it may help in some way.

The difference is subtle. I think that both your examples work, and neither of them hits me as odd.

Let me focus on the case where the duration is of the form ~ない. I think that in this case, うちに is usually more natural than 間に. The following examples by Oyanagi on the page which Axioplase linked to are very interesting:


I do not agree with Oyanagi that 雨が降らない間に is completely incorrect, but I share the feeling that it is less natural than the other three combinations.

But I think that this tendency is weakened when the duration is of the form ~ていない (or its colloquial contraction ~てない, as in your example).

Also, 知らないうちに and 知らない間に both sound correct and natural to me, and I know that I am contradicting myself. That is why I cannot write anything definite here.

(By the way, 間に is sometimes read as まに instead of あいだに, for example in 知らぬ間に and the idiom 鬼の居ぬ間に洗濯, but I ignored the reading まに for the purpose of this answer because the difference between あいだに and うちに seems already complicated.)

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    It seems to me that 間に read as 'mani' is interchangable with うちに. – user458 Aug 13 '11 at 5:44
  • @sawa: Thanks for the comment. That may be the case, but I am not sure. I will not be surprised if you or anyone else comes up with a case where まに and うちに are not interchangeable. – Tsuyoshi Ito Aug 13 '11 at 13:22
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    Is the 間 in いつの間に interchangeable with うち? – Lukman Aug 13 '11 at 21:49
  • @Lukman: No, it can only be いつの間 (ま) に. So it is an example where まに is not interchangeable with うちに. However, one may argue that this まに is a little different from まに in 知らぬ間に because いつの does not specify the duration. – Tsuyoshi Ito Aug 13 '11 at 22:32

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