also: よんごうびん
noun
720ml bottle (of alcohol)
Specifically a bottle containing 4合 (approximately 720ml) of sake or other alcohol. The term is used in the context of Japanese alcohol bottle sizes.
この日本酒は四合瓶で売られている。
This sake is sold in 720ml bottles.
四合瓶を二本買ってきた。
I bought two 720ml bottles.
一升瓶 is a larger bottle containing 1升 (approximately 1.8L), while 四合瓶 is a smaller 720ml bottle.
Compound of 四 (four), 合 (a traditional unit of volume, about 180ml), and 瓶 (bottle). Literally 'four-gō bottle'.