間(あいだ) — Throughout a Duration

• 子供が寝ている間、仕事をしていた。

  Kodomo ga nete iru aida, shigoto o shite ita.

  I was working the entire time the child was sleeping.

  Both actions (sleeping and working) run in parallel from start to finish.

• 電車に乗っている間、ずっと音楽を聞いていました。

  Densha ni notte iru aida, zutto ongaku o kiite imashita.

  I was listening to music the whole time I was on the train.

  乗っている間 + ずっと聞いていた — both actions run in parallel for the entire ride.

• 夏休みの間、毎日プールで泳ぎました。

  Natsuyasumi no aida, mainichi puuru de oyogimashita.

  Throughout the summer vacation, I swam in the pool every day.

  Noun + の + 間 (夏休みの間): the daily swimming spans the whole vacation period.

• ・Parallel state: Since 間 covers a whole span, the main clause must also be a continuous action/state (していた), not a one-moment event.
• ・Nouns take の: 夏休みの間 (throughout the summer vacation).

Commonly confused with

The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones 間 is tested against.

• 間に (あいだに) — A Point Within a Window
• あとで — After (with a time gap)
• 頃 / ごろ — Around / About (approximate time)
• までに — By / No later than (deadline)
• 〜おきに — The Gap Logic (Intervals)
• たばかり — Just did (subjective recency)
• たところ — Just finished (this very moment)
• ているところ — In the Middle of Doing