noun · a system for warming a building by circulating heat from a central source

北方冬天的屋子里都有暖气。

noun · a radiator or physical device used for heating a room

冬天天气冷，他总是靠在暖气旁边取暖。

noun · heated air or a warm current of air

一打开空调，一股暖气扑面而来。