下功夫 xiàgōngfu to put in effort; to work hard at

How to remember 下功夫: 下 down + 功 achievement + 夫 husband = to put in effort; to work hard at.

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To put in real, sustained effort on something - 在发音上下功夫 (zài fāyīn shàng xià gōngfu) to work hard on pronunciation.
The object goes between: 下了不少功夫 (xiàle bù shǎo gōngfu) put in a lot of effort. Pattern: 在...上下功夫.
功夫 here is 'effort/skill through practice', the same 功夫 as in kung fu; implies patient, deep work rather than a quick push.