時間・時点N3
〜間（あいだ）
during... / while... (whole period)
Structure
V-ている + 間；い形 + 間；N + の + 間
Explanation
Indicates the entire period during which an action or state continues; the main clause is a continuous action or state. Unlike 〜間に, 〜間 emphasizes continuation throughout the whole period, and the main clause is not a one-time action.
Examples
日本にいる間、日本語を勉強していました。
I was studying Japanese the whole time I was in Japan.
夏休みの間、ずっと実家で過ごしました。
I spent the whole summer vacation at my parents' house.
Note
With 〜間 the main clause is continuous; with 〜間に it is a one-time action. Keep the difference in mind.