"One of the absolutely key, most important variables as to whether or not a forest survives and continues is whether local people monitor each other and its use.

VOA: special.2009.10.16

On the other hand, temperature, volume and pressure are variables that are much easier in the lab to keep constant.

另一方面，温度，体积和压强,在实验室中比较容易保持恒定。

麻省理工公开课 - 热力学与动力学课程节选

Now in a stoplight, it only has three, one is tempted to say, variables plainly differing from each other: red, yellow and green we have two ways of thinking about the red light.

交通灯，三种灯，红黄绿，它们的颜色和彼此不能,我们有两种方式认识红灯的意思。

耶鲁公开课 - 文学理论导论课程节选