〜間(に) (~aida (ni)) — during / while

Another action inside a stretch of time — and に changes the meaning.

Formula (सूत्र ढाँचा)

Verb Vている + 間(に)

い-adj い-adj + 間(に)

な-adj な-adj [だ] + な + 間(に)

N N + の + 間(に)

There is a small but important difference between 「〜間」and 「〜間に」.
With に, it marks a single action at some point inside a longer stretch: 「休みの間に、実家へ帰った」= during the holidays (at some point) I went home.
Without に, it marks something that continued through the whole stretch: 「休みの間、ずっと家にいた」= I stayed home the whole holiday.
So use 間に for a one-off action and 間 for a continuous one.

Verbs take the ている-form, い-adjectives attach directly, and nouns need の.

子どもが寝ている間に、そうじをした。

こどもがねているあいだに、そうじをした。

While the child was asleep, I did the cleaning.

How it is built (कसरी बन्यो) 寝る → ている-form 寝ている → attach 間に to it → because of に, it means 'at some point during that time'.

休みの間、ずっと家にいました。

やすみのま、ずっといえにいました。

I stayed home the whole vacation.

How it is built (कसरी बन्यो) 休み is a noun → attach の → here に is not used → so it means 'for the whole time'.

若い間に、いろいろ経験したほうがいい。

わかいまに、いろいろけいけんしたほうがいい。

It's better to experience lots of things while you're young.

How it is built (कसरी बन्यो) 若い is an い-adj → attach 間に straight to it → it means 'within that time'.

Question: 1/3

「留守の間＿、荷物が届いた。」— to mark a one-off action?

💡 Hint: It happened once.