这种方言很难懂。

It was difficult to understand the local dialect.

《牛津词典》

这说明书看起来很难懂。

The instructions look very complicated.

《牛津词典》

他写的书很难懂，他的讲演就更难懂了。

It is difficult to understand his books, much more his lectures.

《新英汉大辞典》

You've read all of one essay and you've read part of another, "Differance," and you've found him very difficult.

一整篇论文和另一篇论文的一部分，《延异》，大家已经发现了，德里达的作品很难懂。

耶鲁公开课 - 文学理论导论课程节选

Indeed, in addition to finding him very difficult you've probably said, "Why does he have to write like that?" In other words, "Yeah, okay. He's difficult, but isn't he making it more difficult than it needs to be?"

事实上，除了发现他难懂以外，你可能会说，“为什么他要这样写？“，换句话说，“是的，他的思想很难懂，但是他这样写不是让他的思想更难懂了吗？“

耶鲁公开课 - 文学理论导论课程节选

And I think that's very important especially with electromagnetism, which is so numb toward if, so abstract and so much math flowing around.

我觉得这是非常重要的,尤其是对于电磁学来说，它是一门很难懂的，很抽象的学科,包含很多数学在里面。

麻省理工公开课 - 媒体、教育、市场课程节选