So, in general what we see, and this is always true if we're comparing the same atom, and in general, if we're comparing different types of molecules, but we know that a single bond is always weaker than a double bond, which is weaker than a triple bond.

通常我们会看到，这对比较相同原子来说总是正确的，通常，如果我们要比较不同种类的分子，但我们知道单键,总是要比双键弱，双键总是要比三键弱。

麻省理工公开课 - 化学原理课程节选

So, the general takeaway message here is that there's two types of sleep.

我们普遍能从中得中的结论是,睡眠有两种。

耶鲁公开课 - 心理学导论课程节选