状语从句包括时间、地点、原因、条件、让步、方式、比较、目的和结果等几类。

1. 时间状语从句

1）as soon as, the moment, immediately, the minute, the second, the instant, every time等连词引导的时间状语从句表示“一…就” , “每次”。

She came to the scene the moment she heard of the accident.

Every time I came to see Mr. Johnson, he is always working on his project.

2）Hardly/ Scarcely… when…; No sooner … than…引导的时间状语从句表示“一…就…”；“刚…就…”。主句要用过去完成时，hardly, scarcely, no sooner 位于句首时，句子要倒装。例：

Hardly had I left my house than it rained.   

No sooner had I  finished my homework than the power failure came.  

         3）when , while, whenever

              When: 某一时刻, 可接延续动词或短暂性动词。

                  e.g: I’ll speak to him when he arrives.

                     The doorbell rang when I was telephoning.
             While: 相当于during that time, 表示一个时间段，故一般只接延续动词.

                           e.g: I was walking along the road while suddenly someone patted me on the shoulder from behind. 

             Whenever: 无论何时

                          e.g: Whenever you say “I love you”, mean it.       

                               Whenever you say “I’m sorry”, look the person right in the eyes.

2. 条件状语从句中

1） if 和unless       if 表示正面的条件，意为“如果”；unless意为“除非，如果不”＝if… not

       You will not be allowed to go into the room unless you show your ticket.

2) as/so long as, on condition that, suppose/ supposing(that), in case (of).., provided that都有“如果，只要，假如，在…条件下”。例：

Suppose/ Supposing (that) we only have three days to live, what shall we do?

In case of fire, ring the alarm bell.

3. 在时间和条件状语从句中，用一般现在时代替将来时。

       We will have an outing if it is fine tomorrow.

4. because, since, as 都可引导原状语从句，because 的语气最强，常用于回答以why 引导的疑问句。Since 表示一种附带的原因，或表示已知的、明显的理由，意为“既然”。As表示的理由最弱，只是对主句的附带说明，重在主句。例：

            Because she was late for more than half an hour, she was not allowed to take part in the exam.

       Since everybody is here, let’s start the meeting

       As I am about to start a journey, I shall not be able to begin the work before I return.

l   注意：because, since, as不可与so连用

 

5 since 和now that 意义相近， 意为“既然”，“鉴于” ，有时省去that 也可表示原因状语。e.g：Now（that）you are old enough to make your own judgment, you should start your own career.

6. in that引导原因状语从句，意为“（原因）就在于”。例

              Theory is valuable in that it can provide a direction for practice.

7．Though, although, even if, even though, as whether…or(not) 可引导让步因状语从句。

       1） though, although 不可与but 连用。

       2） though引导的让步状语从句可倒装。

             Though he was young, he faced the difficult situation calmly.

               = Young as he was, he faced the difficult situation calmly.

       3)  whether …or (not) 引导让步因状语从句,提供两个对比的情况，意为“不管…”

              Whether it rains or not, I shall go out for an outing tomorrow.