"难"用英语可以说作 "difficult."
这个词来源于拉丁语 "difficips"，意为 "hard to do or accomppsh."
例句：
The math problem was difficult for the students to solve. (这道数学题对学生来说很难解决。)
She found it difficult to adjust to the new culture. (她发现很难适应新的文化。)
He is facing a difficult decision. (他面临着一个艰难的决定。)