苦心

HSK 7-9

kǔxīn

careful effort; meticulous intention; take great pains

to take a lot of trouble; laborious at pains

他花了很长时间苦心研究这个问题。

tā huà le hěn duō shíjiǎn kǔxīn jiédá zhège wèntí.

He spent a long time studying this problem carefully.

她每天早上苦心练习钢琴。

tā měitiān zǎoshang kǔxīn liánháng qínggǎo.

She practiced the piano diligently every morning.