天气 (tiān qì) literally combines 天 (tiān), meaning 'sky' or 'heaven', and 气 (qì), meaning 'air' or 'vapor'. Together, they refer to the atmospheric conditions at a particular time and place—such as temperature, precipitation, wind, and cloud cover. It’s a fundamental noun used daily in conversation, forecasts, and casual observations.

This word is neutral in register and appears frequently in questions (e.g., '今天天气怎么样？'), weather reports, travel planning, and small talk. Unlike English, Chinese doesn’t use articles with 天气—it stands alone without 'the' or 'a'. It’s uncountable and never pluralized; modifiers like 很好, 很差, or 变化多端 describe its state instead of changing the noun itself.