~の間 (while/during)

The noun 間 ('interval, duration, while') used as a subordinate-clause or noun-attached temporal frame: [N or clause]+の間 = 'while X / during X / for the period of N.' Marks an extended time span. Without に it emphasizes the stretch of time itself; with に (の間に) it points at a moment within that stretch. 夏休みの間 ('during summer break'), 話している間 ('while talking'), 三時間の間 ('for three hours').