天空 (tiān kōng) literally combines 天 (tiān), meaning 'heaven' or 'sky', and 空 (kōng), meaning 'empty' or 'void'. Together, they form the standard, neutral noun for 'sky' — the expanse of air and clouds above the earth. Unlike more poetic or literary terms like 苍穹 (cāng qióng) or 青天 (qīng tiān), 天空 is widely used in everyday speech, weather reports, children’s books, and descriptive writing.

This word appears frequently in contexts involving weather, nature observation, aviation, photography, and basic geography. It’s commonly modified by adjectives (e.g., 蓝色的天空 'blue sky'), measure words (e.g., 一片天空 'a stretch of sky'), or verbs like 看 (to look at) and 飞过 (to fly across). While it can appear in metaphorical expressions (e.g., 心中的天空 'the sky in one’s heart'), its primary use remains concrete and visual — referring to the visible atmospheric dome overhead.