～間に
during / while
～間に（あいだに）uses the noun 間 (“interval”) to mean “during / while”: at some point within the span of X, the main event happens. It typically follows a Verb in ている-form (寝ている間に) or a Noun + の (夏休みの間に).
The particle に matters: ～間に means the main action happens at a point within the span, while ～間 without に means it continues throughout the whole span. And unlike ～うちに, which urges acting before the condition changes, ～間に is a neutral statement about timing.
1. While someone is doing something
With ている + 間に, one action provides the time frame, and another action takes place inside it.
赤ちゃんが寝ている間に家事をする。
“I do the housework while the baby is sleeping.”
- 赤ちゃん（あかちゃん）= baby
- が = subject marker
- 寝ている（ねている）= is sleeping
- 間に（あいだに）= during, while
- 家事（かじ）= housework
- を = object marker
- する = do
2. During a period (noun + の間に)
With a noun describing a period, の間に means something happened at some point within that period.
夏休みの間に、本を三冊読んだ。
“During the summer vacation, I read three books.”
- 夏休み（なつやすみ）= summer vacation
- の = links the noun to 間に
- 間に（あいだに）= during
- 本（ほん）= book
- を = object marker
- 三冊（さんさつ）= three volumes
- 読んだ（よんだ）= read
How to form it
Verb ている + 間に / Noun + の + 間に
- 寝る（ねる）= to sleep → 寝ている間に（ねているあいだに）= while (someone) is sleeping
- 待つ（まつ）= to wait → 待っている間に（まっているあいだに）= while waiting
- 夏休み（なつやすみ）= summer vacation → 夏休みの間に（なつやすみのあいだに）= during summer vacation
Key idea
～間に draws a time bracket and drops one event inside it. Keep the に: with it, the event happens at a point within the span; without it, the second action lasts the entire span.
Other N3 grammar
Updated .