Common room and Restroom

Common room noun - A sitting room (usually at school or university).

Restroom and common room are semantically related in recreation room topic. In some cases you can use "Restroom" instead a noun phrase "Common room", when it comes to topics like rec room.

Restroom noun - A room furnished with a fixture for flushing body waste.

Common room and restroom are semantically related in recreation room topic. You can use "Common room" instead a noun "Restroom", if it concerns topics such as rec room.