晴天 literally means 'clear sky day' — 晴 (qíng) means 'clear, sunny' (referring to cloudless weather), and 天 (tiān) means 'sky' or 'day'. Together, they form a compound noun meaning 'sunny day', describing a day with abundant sunshine and no rain or clouds. It’s a neutral, commonly used term in daily conversation, weather reports, and informal writing.

This word is often used when planning outdoor activities, checking the forecast, or expressing mood — for example, people might say '今天是晴天' ('Today is a sunny day') to note favorable conditions. Unlike more literary or poetic terms like 艳阳天 (yàn yáng tiān, 'brilliant sunny day'), 晴天 is straightforward and appropriate for all registers — from children’s speech to formal announcements. It contrasts directly with words like 雨天 (yǔ tiān, 'rainy day') or 阴天 (yīn tiān, 'overcast day').