So, for example, we have this average level, and then it can go high where we have the peak, or it can go very low. We can also discuss sound waves, so again it's just the periodic variation of some property -- in this case we're talking about density, so we have high density areas and low density areas.

例如这是平均位置，在峰的位置水位高，在谷水位低，我们也可以,讨论声波它也是某种,量的周期变化，在这里我们,讨论的是密度,我们有高密度区和低密度区。

麻省理工公开课 - 化学原理课程节选

We can talk about the wave function squared, the probability density, or we can talk about the radial probability distribution.

我们可以讨论它,波函数的平方，概率密度，或者可以考虑它的径向概率分布。

麻省理工公开课 - 化学原理课程节选

Think of anything else with the density goes down when it freezes, and think about where we would be if that wasn't the case.

想想有没有其他的物质,在降温时密度会变大，再想想如果不是这种情况,我们将会怎么样。

麻省理工公开课 - 固态化学导论课程节选

Local Government Association (LGA) research suggests that one-in-three councils are worried about the density of fast food outlets.

BBC: Town halls call for more power over High Streets

In Orkney, some organic farmers produce salmon at about half the density of conventional farms, without toxic chemicals or colourings.

ECONOMIST: Pressure is mounting to do something about salmon farms

Even without legislation, some experts note that women can ask about their breast density, since radiologists routinely report that information to physicians.

WSJ: The Latest Mammogram Controversy: Density