The difference in the apparent position of the cosmic masers lets astronomers measure their distance from the Earth.

VOA: special.2009.01.20

And to measure the intensity of unequal sharing, we take the difference in electronegativity, which I am going to use the Greek symbol chi for.

要度量非平均的程度，我们考虑电负性的差异，我要用希腊语第22个字母chi来表示电负性。

麻省理工公开课 - 固态化学导论课程节选