困倦 is an adjective meaning 'drowsy' or 'sleepy' — a physical state of tiredness that makes you want to sleep. It combines two characters with overlapping meanings: 困 (kùn) means 'tired', 'exhausted', or 'trapped', and 倦 (juàn) means 'weary', 'fatigued', or 'bored from overuse'. Together, they intensify the sense of mental and physical exhaustion, often implying a deep, heavy sleepiness rather than mild tiredness.

This word is commonly used in formal and semi-formal contexts — in health advice, workplace communication, or daily conversation about rest needs. Unlike colloquial terms like 想睡觉 (want to sleep) or 犯困 (suddenly feel sleepy), 困倦 carries a more objective, descriptive tone and often suggests prolonged lack of rest or sustained mental effort. It’s frequently paired with verbs like 感到 (feel), 出现 (appear), or 缓解 (relieve), and appears in phrases like 困倦感 (feeling of drowsiness) or 困倦乏力 (drowsy and weak).