I want to give you a heads up; you're getting some serious firepower this term.

我有言在先;,这个学期你们都需要抵挡住非常强的火力。

麻省理工公开课 - 计算机科学及编程导论课程节选

but you have a prior engagement and you really must be going, you can say,

但是你已有约在先，你真的必须走了，你可以说，

I wish 课堂 - SpeakingMax英语口语达人

But Patrick knows Steven pretty well; he knows those guys who run Coca-Cola are pretty smart guys, so Patrick knows that the guy who runs Coca-Cola is going to anticipate that the guy who runs Pepsi is gonna cheat on the guy who runs Coca-Cola, and hence the guy who runs Coca-Cola is going to play a best response to Patrick's cheat on quantity.

但是帕特里克也很了解史蒂文,他知道可口可乐的经理都很精明,帕特里克知道可口可乐的经理会预料到,帕特里克会违约,因此可口可乐的经理就会寻找最佳对策,因为帕特里克违约在先

耶鲁公开课 - 博弈论课程节选