‘空气’ (kōng qì) literally combines ‘空’ (kōng), meaning ‘empty’ or ‘sky,’ and ‘气’ (qì), meaning ‘air,’ ‘gas,’ or ‘vital energy.’ Together, they form the standard, neutral term for ‘air’ — the invisible mixture of gases (mainly nitrogen and oxygen) that surrounds Earth and enables breathing. Unlike the more abstract or philosophical uses of ‘气’ alone (e.g., in ‘qi’ energy), ‘空气’ refers specifically to physical atmospheric air.

This word is commonly used in everyday contexts related to environment, health, and weather — such as discussing air quality, fresh air, polluted air, or indoor ventilation. It appears frequently in public health announcements, weather reports, and environmental education. While ‘气’ by itself can mean ‘air’ in poetic or abbreviated speech (e.g., ‘吸气’ — ‘to inhale’), ‘空气’ is the full, unambiguous noun required in formal or descriptive usage.