叹 is a simplified Chinese hanzi, listed here under the keyword “sigh”. It is built from 口 (mouth) and 又 (and). It appears as a component in 3 other characters in this index.
On KumiJi Glyph Explorer, open the parts search and type “mouth” + “and”. 叹 is among the results, together with every other character containing the same shapes.
Open 叹 in the interactive kanji search
to expand every part down to its smallest pieces, add your own names and mnemonic stories,
or search for other characters by their parts.