A lecture room or lecture hall: a room in a school or university where lectures are held (often used for larger or more formal classes).
次の講義は3号館2階の講義室で行われます。
The next lecture will be held in the lecture room on the second floor of Building 3.
講義室が満席だったので、オンラインで視聴した。
The lecture room was full, so I watched it online.
先生は講義室の前方でスライドを使って説明を始めた。
The professor began explaining with slides at the front of the lecture room.