緩
カン, ゆる.い, ゆる.やか, ゆる.む, ゆる.める, ひろ

slacken, loosen, relax, lessen, be moderate, ease

JLPT1 G7 S15 F933

As per 爰# (twist about) + 糸 thread → twist knotted threads in loosening them → *loose*; *slack*; *relieve*; *relax* → *gentle* (curve etc.); *slow*.

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