They run from nine in the morning through four in the afternoon with multiple sections through the middle of the day, which are the most popular sections.

早上有9个课程,到下午有4个课程,而中午也有几个，那些都是很受欢迎的课程。

麻省理工公开课 - 固态化学导论课程节选

That's, there are whole courses on that, there's some great courses here on that, it takes some mathematical sophistication, we're going to push that off a little bit.

有一些课程是专门讲这个的，那些课一般都涉及，一些复杂的数学问题，我们只是简单的讲一些基础知识。

麻省理工公开课 - 计算机科学及编程导论课程节选