惋惜 (wǎn xī) is a formal, literary adjective meaning 'to regret / feel sorry for' a loss or missed opportunity, often with sympathy for someone else's situation. It is more formal and emotionally weighty than 可惜 (kě xī 'it's a pity'), and unlike 遗憾 (yí hàn), which can be a personal regret, 惋惜 focuses on regretting something that is a pity for someone or something else. Use it in written or serious contexts.