Practice JLPTHow to tell them apart
うちに focuses on doing something before a changing situation ends, so it carries a sense of urgency or a limited window, like 休みのうちに寝ておく. 間に simply marks an action that occurs within a defined time span between two points, with no urgency. Swapping them is unnatural when the sentence stresses that you must act before the opportunity slips away, since 間に would sound like a neutral timeframe rather than a closing window.
- うちに Use うちに when you want to act before a situation changes or an opportunity passes.
- 間・あいだ(に) Use 間に when you simply describe something happening within a defined time span.
| Grammar point | Meaning | JLPT level |
|---|---|---|
| うちに uchini | While; before (an opportunity passes) | N3 |
| 間・あいだ(に) aida ni | During/While | N5 |
うちに uchini
While; before (an opportunity passes)
While; before; during | During a period when a certain situation remains in effect.
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休みのうちによく寝ておきます。
I’ll sleep a lot during the vacation.
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何もしないうちに今年も終わった・終わりました。
Before I achieved anything, the year has ended.
間・あいだ(に) aida ni
During/While
During (the time when); while | The space between two temporal or physical points.
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スミスさんは日本にいる間英語を教えていました。
Mr. Smith was teaching English (all during the time) while he was in Japan.
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中川さんのお母さんは中川さんがパリに留学している間に病気になりました。
Mr. Nakagawa's mother become ill while he was studying in Paris.
うちに and 間・あいだ(に) are JLPT N5–N3 grammar points that Japanese learners often mix up. This page compares them side by side — meanings, usage and example sentences — so you can tell them apart.