爱思英语编者按：虚主语（dummy subject）是英语写作中需要避免的陷阱之一。

Writers, especially beginning writers, are often cautioned against using passive voice in their writing because its use slows down the pace.
由于被动语态会影响节奏，作者们(特别是初学者)经常被警告不要使用它。

Another construction that can make your writing plod is the dummy subject.
还有一种结构也会让你的文章变得拖沓，它就是虚主语。

When we use the words it and there to begin a sentence without a referent (a noun the pronoun is referring to), we’re using a dummy subject.
虚主语是指句子开头的it或there没有指代物（it、there指代的名词）。

In this pair of sentences:
下面两个句子中：
I went to see Fantastic Four 2 over the weekend. It was fun, but mostly forgettable.

“It” refers to the movie Fantastic Four 2. The pronoun has a referent.
It指代电影《神奇四侠2》。这个代词有指代物。

In this sentence, however:
但这个句子里：
It is apparent that oil reserves will be exhausted by 2050.

“It” has no referent, and is therefore a dummy subject.
It没有指代物，因此它是虚主语。

The same thing happens frequently with there:
这种情况也经常发生在there开头的句子上：

There are several ways in which you could begin.
There are five stages of grief.

Dummy subjects are just one of many problems that weaken your writing by making it vague, fuzzy, and indefinite. The sentences above can be reconstructed with stronger, more definite subjects:
虚主语是让你的文章变得含糊不清的诸多原因之一。上面的句子可以用更有力、更明确的主语加以改写：

Some experts warn that our oil reserves will be exhausted by 2050.
You could begin in one of the following ways: (followed by a list).
Elisabeth Kubler-Ross identified five stages of grief in her book On Death and Dying.

In general, unless you don’t know who is performing an action, or you want to emphasize the action of the sentence for some reason, you should avoid dummy subjects.
通常情况下，除非你不知道动作由谁做的，或是出于某种原因想要强调动作本身，否则你应该避免使用虚主语。