No, we call that work positive work. All right, so that means we need to put a negative sign right here, by convention.

历史上有过不同的习惯，这里我们规定,如果环境对系统做功。

麻省理工公开课 - 热力学与动力学课程节选

There's no language in the world that has a rule that says the fifth word has to be a verb.

世界上并没有语言规定,说第五个词必须是动词

耶鲁公开课 - 心理学导论课程节选

Slaves can't do that legally, but freedmen can.

法律上规定奴隶不行，但是自由人可以。

耶鲁公开课 - 新约课程节选

Convention, OK, this negative sign is just a pure convention. You just got to use it all the time. If you use an old textbook, written when I was taking thermodynamics, they have the opposite convention, and it's very confusing. But now we've all agreed on this convention, and work is going to be with the negative sign here.

系统对外界做功的符号为负,这就是我们,在本课中的规定，纯粹出于统一符号的需要，有些教科书中，可能会使用相反的符号规定,注意不要混淆了，这门课上,我们将一直使用。

麻省理工公开课 - 热力学与动力学课程节选

By the way, I didn't tell you this but I think you know that I picked my origin to be here and measured y positively to be upwards and I called that 15 meters.

顺便说一下,虽然我没明确指出,但我想你们应该都知道,我把原点取在这里,并规定y的正方向朝上,我设把这里的高度为15米

耶鲁公开课 - 基础物理课程节选