‘恒温’ literally means ‘constant temperature’ — 恒 (hénɡ) means ‘permanent’ or ‘unchanging’, and 温 (wēn) means ‘temperature’ or ‘warmth’. Together, they form a compound noun describing a stable, unfluctuating thermal condition. This term is widely used in scientific, technical, and everyday contexts to refer to systems or environments that maintain a fixed temperature regardless of external changes.

In biology, ‘恒温’ most commonly describes animals — specifically endotherms like birds and mammals — whose bodies regulate internal temperature independently of the surrounding environment. It contrasts with ‘变温’ (biàn wēn), meaning ‘variable temperature’, which applies to reptiles, amphibians, and fish. You’ll also see ‘恒温’ in appliance labels (e.g., 恒温空调), laboratory equipment (恒温箱), and pet care (e.g., for reptile enclosures needing precise heating control).