有同学问到了一个句子：Women with babies peer nervously from behind bedsheets. 如何理解其中的from behind用法？

from behind XX是英文里面一个常见搭配，意思是“从……后面”，比如：There's a man watching us from behind that fence. 有个男人从那道篱笆后面在看我们。

这名同学关注的核心其实是这个问题：为什么两个介词可以连用？实际上英语里面两个介词连用的情况非常多，这在语法上称为“双重介词”（double preposition）。英语中的双重介词一般用来表示物体的位置或者运动关系。

除了刚刚提到的from behind，还有from below, out of, from beneath, across from, up from等等，举几个例子：

Germany's rate has also risen sharply, up from 3 percent to 4.5 percent. 德国的利率也在猛涨，由3％涨至4.5％。

He pulled out an old photo album from beneath a pile of books. 他书堆下面抽出一本旧相册。

They parked across from the Castro Theatre. 他们将车停在了卡斯特罗剧院对面。

除此上面这几个之外，还有一个特殊的双重介词：onto，它等效于on to，比如：As he got onto the plane, he asked me how I was feeling. 句子相当于：As he got on to the plane, he asked me how I was feeling.