苦功的英文：
hard work; painstaking effort

参考例句：

His painstaking to attain his goal in life is praiseworthy.
他为实现人生目标所下的苦功是值得称赞的。

Because the Chinese language is harder to learn and master except for the stout-hearted.
因为中文是一种较难学，较难驾驭的语文，除了肯下一番苦功去学的人。

I said flatly it was not worth my while to face the grind since I was not going in for teaching.
我老实回答她，既然我将来不打算教书，就犯不上下这番苦功。

hard是什么意思：
adj. 硬的，坚固的；困难的；有力的；冷酷无情的
adv. 努力地；困难地；严重地，猛烈地

It is hard to conclude.
这很难断定。

It is blowing hard.
风刮得很大。

It was sleeting hard.
雨雪霏霏。

work是什么意思：
n. 工作；职业；工厂；工作地点；产品；功；操作；作品；工程
v.（使）工作；操作；运作；起作用；使缓慢前进；经营

the works of a clock
钟的活动部件

conscientious work
本着良心做的工作

The work is not advancing.
工作没有进展。

painstaking是什么意思：
n. 辛苦；勤勉
adj. 辛苦的；勤勉的；小心的

The experts did a painstaking sifting of debris.
专家们对岩屑进行了煞费苦心的研究。

Solvable or comprehensible only with painstaking effort.
难理解的只有经过刻苦的努力才能解决或理解的

It was this painstaking apprenticeship that gave Van Gogh mastery of painting.
这种辛勤的练习，使梵高精通了绘画技巧。