嘆 (readings: たん, なげ; Japanese kanji) means “Sigh / Lament / Moan / Grieve”. It is a Jōyō kanji taught in Japanese secondary school (junior & senior high) — the 高手 · Master tier beyond the grade 1–6 Kyōiku set, and appears in words such as 感嘆 (admiration).
What does 嘆 mean?