By "difficult," it is meant, I think, well, first of all that it is in some sense set apart from common speech, as a specialized and highly self-conscious use of language.

艰深“的意思，我认为，首先，某种程度上它是和平时谈话有所不同的，专业性极强，对语言运用自知也很高。

耶鲁公开课 - 现代诗歌课程节选

But in particular, it's going to use self to refer to that instance.

好，那么让我换种，稍微不同的说法吧,我有一个类的定义。

麻省理工公开课 - 计算机科学及编程导论课程节选

Virtue means for him a kind of manly self-assertion, audacity, ruthlessness, a reliance on one's own arms and calculated use of cruelty to achieve one's ends.

美德对他而言,是一种具男子气概的自作主张，胆大，冷酷，自助，且还会算计使用残忍手段,来达致目标。

耶鲁公开课 - 政治哲学导论课程节选

You can also use it in self-defense.

你也可以用它自卫。

哈佛公开课 - 幸福课课程节选

In this mode either the students can self-study, Work on their own, or often Prof. Perdue will use These materials in the classroom and use them to Launch a larger discussion about what the students understand from these materials.

在这种模式下，学生可以自学，或者Peter，Perdue教授也经常拿这些,当作课堂讨论的材料,激发大家的讨论,看学生从中学到了什么。

麻省理工公开课 - 媒体、教育、市场课程节选