狀語從句的省略是指使語言的精煉將狀語從句進行簡化。需滿足兩個條件: 1.主句和從句的主語一致，或從句主語為it；2. 從句主要動詞是be的某種形式。

例如：

When ( the museum is ) completed , the museum will be open to the public next year .

He’ll go to the seaside for his holiday if (it is ) possible.

另外，比較狀語從句經(jīng)常省略。

例如：

The higher the temperature (is), the greater the pressure (is ).

狀語從句的"簡化"現(xiàn)象常存在于以下五種狀語從句中:

①由if, unless等引導的條件狀語從句;

②由although, though, even if / though等引導的讓步狀語從句;

③由when, while, as, before, after, until / till等引導的時間狀語從句;

④由as, as if等引導的方式狀語從句;

⑤由as, than等引導的比較狀語從句。下面針對這五種情形作一歸納。

(1)當狀語從句的主語是it,且謂語動詞是be時,it和be要完全簡化掉。

例如:

If (it is) possible, he will help you out of the difficulty.
如果可能的話,他會幫你擺脫困境。

You must attend the meeting unless (it is) inconvenient to you.
除非情況對你來說不方便,否則你必須出席這次會議。

(2)當狀語從句的主語和主句的主語一致時,從句可以將主語和be動詞簡化掉。常用于以下幾種情形:

a.連詞+形容詞

As (he was) young, he learned how to ride a bike.
他小時候就學會了騎自行車。

Work hard when (you are) young, or you'll regret
.
少壯不努力,老大徒傷悲。

b.連詞+名詞

Although (he was) a farmer, now he is a famous director.盡管他曾是個農(nóng)民,而現(xiàn)在是位著名的導演了。

c.連詞+現(xiàn)在分詞

Although (he is) doing his best in maths these days, he has still got no good marks.盡管近來他一直在學數(shù)學,但他仍然沒有取得好成績。

d.連詞+過去分詞

He won't go there with us unless (he is) invited.
除非受到邀請,否則他不會和我們一道去那里。

The concert was a great success than (it was) expected.
這場音樂會出乎意料地取得了巨大成功。

e.連詞+不定式

He stood up as if (he were) to say something.
當時他站起來好像要說什么。

He wouldn't solve the problem even if (he were) to take charge.
即使他來負責,他也解決不了這個問題。

f. 連詞+介詞短語

She looked anxious as though (she was) in trouble.
她看上去很焦急,好像遇到了麻煩。

He had mastered the English language before (he was) in the USA.
他到美國之前就懂英語了。

注意:當從句主語和主句主語不一致時,從句部分要么用完全形式,要么用獨立主格結(jié)構(gòu)來表達。例如:

When the meeting was over, all the people went out of the meeting-room.
當會議結(jié)束時,人們都走出了會議室。