noun
studio apartment; one-room apartment
A small apartment where the main living area and bedroom are combined into a single room, with a separate bathroom and sometimes a small kitchenette. Common in urban Japan.
wasei-eigo (Japanese-coined English), from one room
東京でワンルームを借りるのは高い。
Renting a studio apartment in Tokyo is expensive.
彼は駅近のワンルーム
He lives in a studio apartment near the station.