効
コウ, き.く, ききめ, なら.う

merit, efficacy, efficiency, benefit

JLPT2 G5 S8 F538

As per 交# (twist/cross) + 力 power/energy → crossing of energy back and forth in effective cooperation → *work well*; *effect*; *do one's best*. *Take after* is a borrowed meaning via 效.

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