Sometimes they are difficult to understand
有时梦是很难理解的。
Highly abstract or theoretical;abstruse.
难理解的极度抽象的或理论上的
a muddled explanation which was scarcely intelligible
难以理解的胡涂解释.
Difficult to perceive or grasp by the mind.
难懂的难以理解的或隐晦难懂的
It is difficult to understand comprehend his Behavior
很难理解他的行为。
It's hard for me to make out what he was saying.
我很难理解他说的话。
Your meaning is too dark for me.
你的意思我很难理解.
She had great difficulty in understanding him.
她很难理解他说的话。
What you wrote is out of my range
你所定的我难以理解。
difficulties within/beyond sb's grasp
某人能[不能]理解的困难
unfathomablemotives, mysteries
难以理解的动机、 奥秘.
An instance of being imperfectly known or difficult to understand.
难于理解的不被清楚知晓或难于理解的例子
Not easy to understand or analyze.
难懂的难于理解或分析的
Philosophy: unintelligible answer to insoluble problem.
哲学：是对难以解释的问题作出难以理解的答案。
difficult to understand or explain because there are many different parts
（因复杂）难于理解或解释的
Recommendations to resolve the difficulties with reading comprehension;
如何解决阅读理解中的难点(英文)
beyond belief or understanding.
难以置信或者难以理解。
It' s very difficult to understand the mentality of people who say such things.
很难理解讲这种话的人的心理状态。