Isaiah in this passage is describing a crucial moment in his career, his career as a prophet: the moment in which his lips are cleansed and he is empowered -- divinely empowered -- to speak prophetically.

在这一段里艾赛亚描述了一个他事业上至关重要的时刻，作为一个预言家：在这个时刻他的嘴唇被清洁干净,他被神圣得授权来预言。

耶鲁公开课 - 弥尔顿课程节选

But before you even do that, I want to define for you an important concept, which is the velocity at a given time, v .

但在这之前,我要给你们定义一个重要的概念,也就是给定时刻的瞬时速度v

耶鲁公开课 - 基础物理课程节选