天亮 literally means 'sky brightens' — 天 (tiān) means 'sky' or 'heaven', and 亮 (liàng) means 'bright' or 'to become bright'. Together, they form a noun referring to the moment when daylight first appears at the end of night, i.e., dawn or daybreak. It marks the natural transition from darkness to light and is often used in descriptions of time, weather, or daily rhythms.

This word is neutral in register and commonly appears in both spoken and written Chinese — in storytelling, weather reports, poetry, and everyday conversation. Unlike abstract time terms like 早晨 (morning), 天亮 emphasizes the visual and atmospheric change: the sky gradually lightens, stars fade, and the world becomes visible again. It can also appear in idiomatic expressions like 天亮之前 ('before dawn') or in compound phrases such as 天亮了 ('It’s dawn now'), which signals the start of a new day or a turning point.