noun
A commercial or communal bathhouse where people pay to bathe. Historically common before home baths became widespread; still found in some neighborhoods and hot-spring towns.
江戸時代には町にたくさんの湯屋があった。
In the Edo period, there were many public bathhouses in town.
近所の湯屋は朝早くから開いている。
The neighborhood bathhouse opens early in the morning.
noun
bath building (in a shrine or temple)
A building with a bath located within a shrine or temple grounds, often used for ritual purification or for the use of pilgrims and monks.
そのお寺の湯屋は参拝者も利用できる。
The temple's bath building can also be used by worshippers.
Compound of 湯 (yu, 'hot water') and 屋 (ya, 'shop' or 'building'). The spelling 斎屋 uses 斎 ('purification') for the shrine/temple sense.