氧气 (yǎng qì) is a compound noun meaning 'oxygen'—the colorless, odorless gas essential for human and animal respiration. The first character, 氧 (yǎng), is the chemical element name for oxygen, derived from the radical 气 (qì, 'air/gas') plus the phonetic component 羊 (yáng). The second character, 气 (qì), means 'air', 'gas', or 'vital energy', reinforcing the gaseous nature of the substance. Together, they literally mean 'oxygen gas'—a precise scientific term used in medical, environmental, and everyday contexts.

You’ll encounter 氧气 in hospitals (e.g., oxygen tanks), science classes, fitness discussions (e.g., oxygen intake during exercise), and air quality reports. Unlike the broader philosophical or traditional Chinese medicine sense of 气, 氧气 refers strictly to the chemical element O₂ and carries no metaphysical connotation. It’s always used as a concrete, countable noun in scientific contexts, though it’s uncountable in English ('oxygen', not 'oxygens').