a room used for living in a residence (e.g., living room, bedroom); a habitable room (term often used in real estate/architecture)
このマンションは居室が3つあり、家族向けだ。
This apartment has three rooms for living and is suitable for a family.
賃貸契約書には居室の面積が明記されている。
The rental contract clearly states the floor area of the living rooms.
居室と書斎を分けて使いたいと考えている。
I want to use separate rooms for living and for a study.