outside of 的意思

在一本書見到有句句子：

It is pointless to take English classes yet never speak it outside of class.

這裡的outside of ，可否用outside 代替？

答案是可以也是不可以。可以，因為意思上outside class即教室以外，但outside of 有另一種意思，就是apart from.　可參這裡：　http://english.stackexchange.com/questions/9700/outside-or-outside-of

Outside of tends to be more commonly used in the US than in Britain, where outside usually suffices, but, like its cousin off of, it is colloquial and not recommended for formal writing. … The adverb outside is not problematic when referring to physical space, position , etc. (I‘m going outside), but the compound preposition outside of is often used as a colloquial (and often inferior) way of saying except for, other than, apart from (outside of what I just mentioned, I can’t think of any reason not to). Besides possibly sounding more informal than desired, outside of may cause misunderstanding by suggesting physical space or location when that is not the point to be emphasized, or when no such sense is intended — consider the ambiguity in this sentence: outside of China, he has few interests. Does this mean that his primary interest is China? Or does it mean that whenever he is not in China, he has few interests?