when

The word 'when' is an adverb used to inquire about the time at which an event occurs or has occurred.

• When will you arrive? — あなたはいつ到着しますか？
• I remember when we first met. — 私は私たちが初めて出会ったときを覚えています。

'When' as a conjunction is used to connect clauses, typically indicating the time at which something happens.

• Call me when you get home. — 帰ったら私に電話して。
• He reads a book when he has free time. — 彼は暇なときに本を読みます。

'When' as a pronoun refers to a specific time or period previously mentioned or understood.

• Do you remember that time when we traveled together? — 私たちが一緒に旅行したときを覚えていますか？
• I will tell you when I know the details. — 詳細がわかったら教えます。