Photocopiers print in two dimensions. Now,imagine how this would work for three dimensions.

VOA: special.2010.10.29

For most of us, we can go up to three dimensions because we know we live in a three-dimensional world.

对于大多数人来说,我们最多可以考虑三维,因为我们生活在一个三维世界

耶鲁公开课 - 基础物理课程节选

There's only one occasion where it helps to go to three dimensions because there are certain things you can do in 3D you cannot do in less than 3D.

只有一种情况下进入三维是有意义的,因为有些事情你能在三维空间内完成,但低于三维就做不到了

耶鲁公开课 - 基础物理课程节选

So that you take every sodium and you count all of its nearest neighbors, next nearest neighbors, next next nearest neighbors, not only on a line but in the plane and above and below in all three dimensions and go through that calculation, it is even more negative.

你考虑到每一个钠原子,你要考虑到它最近的原子，第二近的原子，第三近的原子，不是在一条线而是在一个面上,以及面上与面下的三维空间,再完成计算，这将会更负。

麻省理工公开课 - 固态化学导论课程节选

And then, if you go the real sodium chloride crystal and you do this same calculation but in three-dimensions.

接下来，如果回到实际的氯化钠晶体中,你们做同样的计算,但是是在三维中。

麻省理工公开课 - 固态化学导论课程节选