あいだ and うち
This page explains 間 and 内に, as well as attempts to explain the differences between the two.
あいだ
During the time of..
Plain non-past form verb/い Adjective + あいだ
Noun + のあいだ
な Adjective + なあいだ
間(あいだ) is a noun meaning “Span”, in this case a “span of time”.
- 長い間 – a long (span) time.
- この間 – That (span of) time (not long ago).
An application of this is to talk about a particular time period when something is happening
- 学校に行っている間勉強する
Study while going to school. - 休憩している間に寝る
Sleep while taking a break. - 寝ている間にいい夢を見た
I had a nice dream while sleeping. - 夜の間に自転車が盗まれた
My bike was stolen during the night. - 会っていない間に変わった
He has changed during the time I haven’t seen him.
間・間に
Like a lot of other time phrases, に is optional with 間 as well.
There is a tiny difference in nuance:
- 学校にいる間勉強した
Studied while at school. (All the time) - 学校にいる間に勉強した
Studied at some point while at school
In other words, に reduces the action to occurring at a sometime during the span, much like まで and までに
This usage of に is much less strict than with まで、and may be omitted/not omitted “incorrectly”.
うち
While you can
Plain non-past form verb/い Adjective + うち
Noun + のうち
な Adjective + なうち
内（うち) also indicates a span of time. However, this span of time, as opposed to 間, 内 is shorter and more temporary, and has a feeling of “while you can“.
It is frequently (not always) used with plain negative verbs. Additionally, it is more frequently used with adjectives than 間.
内 does not come after negative progressive tense words. i.e. “It doesn’t” instead of “it isn’t”
Examples
- 雨が降らないうちに帰ろう
Let’s go home while it doesn’t rain. (降っていないうちに is wrong) - 眠たいうちに寝よう
Let’s sleep while we’re sleepy. - 帰られるうちに帰る
I’m going home while I can. - 先生が嬉しいうちに聞く
Ask while the teacher is happy. - 彼が帰らないうちに遊ぶ
Play while he is not at home.
Expressions
- 一瞬のうちに
In an instant - 瞬くうちに
In the blink of an eye.
Comparison
間:
- Describes what happens during a time.
- Should not be used with time sensitive actions
- Verb ない + 間 must describe a past tense event that occurred in a span. *
*my attempt to find a rule, if you find a counter-example, let me know. (がない is different). - May appear as ~ていない間に
内:
- Describes the only time/best time to do an action.
- Used with time sensitive actions. The action must be completed in a specific span of time.
- Sometimes used in less time sensitive cases, but has a “lucky” or “short” nuance to it.
- May not appear as ~ていないうちに (Must be ないうちに）
Everything below this point gets harder and less useful. You may skip it.
That being said, there are some annoying cases where either may be used, with the nuance changing accordingly. Lets look at this example from stack exchange:
晴れている［○間に］［○うちに］作業を終わらせよう。
Versus,
雨が降らない［×間に］［○うちに］作業を終わらせよう。
The difference with 晴れている feels minor to me:
- 晴れているうちに – While it is still sunny.
- 晴れている間に – While it is sunny.
However:
雨が降らないうちに – While it doesn’t rain, finish it. (isn’t raining)
雨が降らない間に – While it didn’t rain, finish it — This is wrong.
The action has not yet occurred and is meant to be completed during the span, which makes 内 the natural choice.
However, 降らない間に may be acceptable if used like:
- 雨が降っていない間に終わらせよう – Let’s finish it during the time it isn’t raining.
- 雨が降らない間に植物が枯れて死んだ – During the time it didn’t rain, the plants withered and died.
For doing an action within a time span (i.e. not simply “occurred” in a time span”)
ない＋うちに 〇
ていない＋間に 〇
ない間に ✖
ていないうちに ✖
More reading here. (Japanese linguistic paper, 12 pages)
References
HiNative (Japanese, about 降っていない・降らないうちに）(Also confirmed with Japanese friends).
Chiebukuro (Japanese) Best explanation of differences.
Linguistic paper
Stack Exchange