‘叹气’ is a verb meaning 'to sigh' — to slowly and audibly exhale air, usually as an expression of emotion. The first character, 叹 (tàn), means 'to exclaim' or 'to utter with feeling', while 气 (qì) means 'breath' or 'air'. Together, they literally convey 'uttering breath', capturing the physical and emotional act of sighing. It’s commonly used to express sadness, disappointment, relief, weariness, or resignation — not just negative feelings, but also quiet acceptance or gentle exhaustion.

This word appears frequently in everyday speech and writing, especially when describing inner states indirectly. Unlike English, where 'sigh' can be a noun or verb, 叹气 functions almost exclusively as a verb in modern Mandarin and is rarely used as a noun without modification (e.g., 叹气声 for 'the sound of sighing'). It often follows subject–verb structure and may be preceded by adverbs like 不禁 (can’t help but) or 深深地 (deeply) to intensify the emotion.