Grammar › N4 · 07 Time, phases & degree
〜あいだ・〜あいだに: while; during
N4 · 07 Time, phases & degree
あいだ means during the whole time something continues, and あいだに means at some point within that time.
Verb ている/dictionary form, noun + の, adjective + あいだ(に). 寝ているあいだ (the whole time asleep) vs 寝ているあいだに (something happens while asleep). Use あいだ with a continuing action, あいだに with a one-time action.
Examples
子どもが寝ているあいだ、本を読んでいました。
I was reading a book while the child was asleep.
留守のあいだに、荷物が届いた。
A package arrived while I was out.