刻苦

他刻苦学习，每天都要复习很多课程。

tā kèkǔ xuéxí, měitiān dōu yào fùshì hěnduō kèchéng.

He studies hard every day, reviewing many courses.

她刻苦工作，总是第一个到办公室。

tā kèkǔ gōngzuò, zǒngshì dìyī ge dào shìfèngjiān.

She is diligent and always arrives first at the office.