熬干 (áo gān) is a compound verb meaning 'to simmer or boil down until completely dried up'—typically referring to liquid being reduced over heat until no moisture remains. The first character, 熬 (áo), conveys prolonged heating, often with effort or endurance (as in 'to stew' or 'to熬 through'), while 干 (gān) means 'dry' or 'dried out'. Together, they emphasize the process and final state: not just evaporation, but thorough, deliberate reduction to dryness.

This term is commonly used in cooking, herbal medicine preparation, and traditional food preservation—especially when making concentrated pastes, dried herbal extracts, or candied fruits. It implies careful control of heat and time; rushing may cause burning rather than clean drying. Though literal, it can occasionally appear metaphorically (e.g., '熬干心血'—'to exhaust one’s energy and resources'), but such usage is literary and rare in everyday speech.