In American English, the saying a hard nut to crack means something hard to understand.

在美英语中，a hard nut to crack意思是很难理的事情。

It is very difficult to understand the subtle economics of drug pricing.

药品定价的经济学原理是很难理的。

Sometimes it is difficult to explain why some men suddenly do the things they do.

有时候，人们那突如其来的行为是很难理的。

Sometimes it's hard to explain why some men suddenly do the things they do.

人们那突如其来的行为有时候是很难理的。

These questions can make it hard to fathom downgrading.

这问题会让你很难理降级的做法。

Look, I know this is hard to understand, but my family, we were raised with this.

知道这很难理，但的家族，们从小就被灌输了这样的思想。

That can make it hard for those not directly involved to understand the gravity of individual cases.

这使得那没有直接参与的人很难理个别案件的严重性。

Uh, it's, I find it difficult to understand what I listen to if I don't read it.

如果不去读，就很难理所听的内容。

If you combine this with an accent that the audience isn't used to, your audience will struggle to understand you.

如果同时你还有一种听众们不太习惯的口音，那么你的听众会很难理你的演讲。

In this episode, I'm going to first talk about why it's so hard to understand native speakers when they speak fast.

在这节课中，将首先谈谈为什么母语人士说得快时很难理他们的意思。

It's not that hard a concept. The left one's on the right, and the right one's on the left; that's all.

没这么难理吧，左边的长右边了，右边的长左边了，就是这样。

The thing that makes this word so hard is the Flap-schwa-Dark L ending.

使这个词如此难理的是 Flap-schwa-Dark L 结尾。

But this is not a difficult book to read or understand.

但这并不是一本难读或难理的书。

That's a really difficult idea to load into your head.

那真是个很难理的概念。

You know, that's something that's hard to make sense of on a normal atheistic picture.

你知道，这在普通的无神论观点中是很难理的。

WHETHER IN SPORTS or politics, it's hard to understand the precise nature of momentum.

— 无论是在体育界还是政治界，都很难理势头的确切性质。

Christina had a hard time conceptualizing her own parents' divorce when she was a young adult.

克里斯蒂娜在年轻时很难理自己父母的离婚。

And the more different an animal is from us, the harder it is to understand their experience.

动物与们的差异越大，就越难理它们的感受。

You guys have noticed: 'vulnerable' is a pretty tough word.

你们已经注意到：“易受伤害”是一个非常难理的词。

If you scored 11 to 20 points, you struggle to make sense of your feelings and find them too overwhelming to deal with.

如果你得了11—20分，你就很难理自己的感觉，觉得它们太难以应对。