惋叹 is a compound verb meaning 'to sigh in regret' or 'to lament with sorrow.' The first character, 惋 (wǎn), conveys deep pity or sorrow for something unfortunate or lost; the second, 叹 (tàn), means 'to sigh' — often expressing emotion aloud. Together, they emphasize an emotional, vocal reaction to disappointment, loss, or missed opportunity, carrying a literary and slightly formal tone. It’s commonly used in written Chinese, storytelling, or reflective speech — less frequent in casual daily talk.

This word evokes a sense of poignancy: not just sadness, but sorrow mixed with helplessness or nostalgia. It often appears when describing reactions to tragic events, unfulfilled potential, or irreversible change — for example, after learning about someone’s untimely death or witnessing the decline of something once cherished. While it can be used alone as a verb, it frequently follows subjects like 他, 我们, or people’s names, and may be modified by adverbs such as 不禁 (cannot help but) or 深深地 (deeply).