狀語從句在主從復合句中修飾主句中的動詞、形容詞或副詞等，按意義可以分為時間、地點、原因、目的、結果、條件、方式、比較、讓步等狀語從句。
一.時間狀語從句。
通常由從屬連詞when, whenever, as, while, before, after, as soon as, till, until, since, once (一旦), hardly……when…, no sooner…….than…; 等引導。例如：
The cyclist started just as the lights changed to green.
Whenever we met with difficulties , they cam to help us.
He didn’t leave his office until he had finished the day’s work.
應注意的問題
1.在時間狀語從句中，通常要用動詞的一般現在時態表示一般將來時態，用一般過去時態表示過去將來時態。但when 引導一般疑問句或名詞性從句時不受上述語法規則的限制，因此，應該加以區分。例如：
When China will enter WTO depends on the bilateral (雙邊的)joint efforts.
Once you understand the rules of the game, you’ll enjoy it.
2.when , while, as 的不同用法。一般說來，當主、從句的動作是同時發生的事，三者可以換用。when 既可以引導一個持續動作，也可以引導一個短暫動作，可用于主句和從句動作同時發生或從句動作先于主句動作;while 引導的動作必須是持續性的，強調主句和從句的動作同時發生，往往側重主句和從句動作的對比;as 用于引導“在某行為的繼續中發生某事”的“繼續之行為”，所以多與過去進行時連用，翻譯成“一邊……一邊……”或者表示動作的變化，翻譯成“隨著……”。
例如：
I hope you’ll think of my words as/when/while you drive on the busy roads.
When he realized it, the chance had been lost.
When he came home, I was cooking dinner.
I was fat when I was a child.
He took a bath while I was preparing dinner.
As I was walking down the street, an American asked me for the directions to the nearest station.
He sang songs as he was taking a bath.
As he gets older he gets more optimistic.
另外還必須注意 when和while 的特殊用法。when 可以表示“就在這時，突然”之意;而while 則可以表示對比的含義，常可譯作“而”。例如：
She thought I was talking about her daughter, ____, in fact, I was talking about my daughter.(NMET95)
A. whom B. where C. which D. while
答案：D. 本句的意思是“她認為我在談論她女兒，然而，實際上，我在談論我女兒。”
再如：
I was about to go to bed when the phone rang a second time.
我正準備去睡覺，就在這時電話鈴又響了。
3.since 和before 的用法區別。兩者都可用于 “It + be + since/ before-從句”的句型，區別在于 since 表示“自從…… 以來”，所在主、從句的謂語動詞的時態關系是：It is/has been some time since sb did something. 而before 的含義則是“(過了多久)才……”,主、從句的時態關系是：It was/ had been some time before sb did sth。 表示過去和將來時，兩者相應的句型分別是：It was some time since sb had done something. 和It will be some time before sb does something. 例如：
It was / had been years before I came back from abroad.
It will be five years before we meet again.
4.一些表示時間的名詞詞組如： the first time, the second time, last time， the moment, the minute，the year, every time, each time , next time, 或副詞immediately, instantly, directly等也可以引導時間狀語從句。例如：
I’ll tell you about it the moment you come.
I recognized her the minute I saw her.
I’m going to see him next time he comes to Shanghai.
He left Europe the year World War II broke out.
I got in touch with him immediately I received his letter.
My sister came directly( = as soon as ) she got my message.
5.till 和until
till 和until 意義相同，多數情況下可以換用，但用以強調，句首多用until; 在強調結構或與not 連用時多用until. 例如：
Nothing can be done till/until the boss returns.
We waited till/until they came back.
Until we know the facts, we can’t do anything about it.
Not until midnight did the noise of the street stop.
6.hardly……when和no sooner……than相當于as soon as 之意，也可引導時間狀語從句。從句謂語動詞用一般過去時，主句謂語動詞用過去完成時。hardly 及no sooner 置于句首時，語氣較強，主句的謂語要部分倒裝。例如：
We had hardly begun when we were told to stop.
= Hardly had we begun when we were told to stop.
The spy had no sooner returned home than he was told to go to another country.
= No sooner had the spy returned home than he was told to go to another country.
二.地點狀語從句。
地點狀語從句由 where和wherever 引導， 在主句前、后都可。where 表示特指，wherever 則表示泛指。但不少學生易將其和定語從句混淆，再者有的同學對地點狀語從句不太注意，所以往往做錯。例如：
You should make it a rule to leave things ___ you can find them again. (NMET99)
A.when B.where C.then D.there
答案：B. 注意它引導的不是定語從句。
After living in Paris for fifty years he returned to the small town ____ he grew up as a child.(NMET 96)
A.which B. where C. that D. when
答案：B. 這是一個由where 引導的定語從句，修飾先行詞the small town.。再如：
Where there is a will, there’s a way.
