松弛
sōng chí · HSK 7
to relax
🎀 松 = loose/slack + 弛 = unstring a bow; together: gone slack, relaxed
弛 carries the bow radical 弓 and originally meant to unstring a bow, letting the tension out. Pair it with 松 (loose, also the pine) and 松弛 names anything that has gone slack: muscles, rules, or a relaxed mood.
松 — tree 木 + public 公
A semantic-phonetic compound: 木 (tree) gives the meaning, while 公 (gōng) hints at the sound. Originally referring to the pine tree, whose loose, spreading needles led to the extended meaning 'loose' or 'relaxed'.