英语从句分类与解析
主句和从句的划分方法是相同的。句子的成分从谓语动词处来划分比较容易。谓语动词前面的部分是主语，后面常接宾语，修饰谓语动词的是状语，修饰主语、宾语的是定语，若谓语是系动词，则系动词后的部分是表语。如：
从句是相对于主句而言的，即它是从属于某一个主句，而不能单独作一个句子。在英语中，主要有三大从句，即名词性从句（包括主语从句，宾语从句，表语从句，同位语从句）、形容词性从句（即定语从句）、副词性从句（即状语从句，包括时间、条件、结果、目的、原因、让步、地点、方式等）。
一、名词性从句 引导这些名词性从句的关联词包括:
从属连词that, if, whether;
连接代词 who,whoever,whom,whomever,which,whichever,what,whatever,whose;
连接副词where, when, why, how。
其中, 从属连词只起连接作用, 在从句中不充当任何句法成分, 而连接代词和连接副词既起连接作用, 在从句中又充当一定的成分.
注意：1.从属连词whether和if都作“是否…”解, 但if不可引导主语从句和表语 从句。whether可与or(not)连用, 而if不可以。 I don't know whether (if) she is at home. Whether she comes or not makes no difference.
2. that和what引导名词性从句的区别: that在从句中不充当成分,而what在从句中充当一定的成分, 如主语、表语、宾语等。that可省略, what则不可省。 He always means what he says. She suggested (that) he do it at once.
3. 同位语从句大多由从属连词that引导, 常跟在下列名词后面, 如fact, idea, opinion, news, hope, belief等, that不可省。同位语从句一般用来解释说明这些名词的具体含义和内容。
二、定语从句 引导定语从句的关联词包括: (1)关系代词:that, which, whose, who, whom, as; (2)关系副词:when, where, why。 关系代词和关系副词在定语从句中都充当一定的句法成分, 关系代词在句中充当动词的宾语时, 一般可省去。
定语从句分为限定性定语从句和非限定性定语从句, 限定性定语从句与主句关系紧密, 为句中不可缺少的部分, 如去掉, 主句意思不完整。非限定性定语从句与主句关系松散, 如去掉, 主句内容仍完整。在书面语中, 非限定性定语从句一般被逗句隔开。非限定性定语从句一般不用that引导。引导非限定性定语从句的关系词不可省略。
I know that he is a man who (that) means what be says.
The gentleman whom (that) she met addressed her with courtesy(礼貌)。
You're the only one whose advice he might listen to.
三、状语从句 在复合句中, 起状语作用的从句称作状语从句。根据语义, 状语从句分为: 时间状语从句、地点状语从句、条件状误从句、原因状语从句、让步状语从句、比较状语从句、目的状语从句、结果状语从句、方式状语从句。状语从句可放在句首或句末。如状语从句位于主语前,一般用逗号将其与主句隔开。
(一)时间状语从句 When you cross a main road, you must be very careful. Until we learn the facts, we can't do anything about it. [提示] 1. when, as, while引导时间状语从句时都可以表示主句的动作与从句的动作同时发生, 即同时性。它们的区别在于: when和as引导的状语从句中的动作既可以是延续性的, 也可以是非延续性的, 即瞬时性的; while引导的状语从句中的动作只能是延续的动作或状态。 当主句和从句中的动作均为延续动作时, 一般用while, 而不用when或as。当表示两个同时发展、变化的情况时, 一般用as, 作“随着…”解。 When she comes, I shall tell her to wait for you. As she got older, she got wiser. While Peter was reading, his wife was cooking. 2. 有些副词和一些表示时间的名词词组也可用作从属连词,引导时间状语从句。如instantly, immediately, directly, the day, every time, the minute, the second, the moment等。
(二)条件状语从句 引导条件状语从句的从属连词有: if, unless, as (so) long as, only if(只要)。
If you don't come on time, we'll start out without you.
As (so) long as you keep on trying, you'll certainly succeed.
Take the raincoat in case it rains.带着雨衣,以防下雨。
(三)原因状语从句 引导原因状语从句从句的从属连词有: becasue, since, as, now(that), in that, considering that等。
Since the speaker can't come, we'll have to cancel the meeting.
Considering he's only been learning English a year he speaks it very well.考虑到他只学了一年英语,他讲得算是很流利了。
We didn't know what to do as we were just visiting there.我们不知道该怎么办,因为当时我们仅仅在那里作访问。
Since it is so hot, let's go swimming.既然天气这么热,我们去游泳吧。
[提示] in that和now(that)的用法: in that引导的从句对主句进行解释和说明,意思是: 在…方面, 在于…; 因为。now(that)表示既然。
Theory is valuable in that it can provide a direction for practice. 理论所以有价值,就在于它能给实践指出方向。
Now (that) the weather has improved, let's go out for a picnic. 既然天气已转好, 我们就出去野餐吧。
(四)让步状语从句 引导让步状语从句的从属连词有: though, although, even if (even though), as, no matter…despite the fact that, in spite of the fact that, while。
Tired as he was, he sat up late.他虽然疲倦,可仍然很晚才睡。
No matter how they slander us, we will never give in.不管他们怎样诽谤我们,我们决不让步。 While I like the color of the hat, I do not like its shape.虽然我喜欢这顶帽子的颜色,但我不喜欢它的形状。
[提示] 一些疑问词在词尾加上ever后, 也可引导让步状语从句,相当于no matter+疑问词。这些词包括: whatever, wherever, whenever, whoever, however。
Whatever he says, don't beleve him. Whoever you are, you must obey the traffic regulations. (五)目的状语从句 引导目的状语从句的从属连词有: so that, in order that, lest, in case, for fear that。
We dare not play jokes on him lest he should become angry.我们不敢开他玩笑生怕他动气。
[提示] so that和in order that的区别: so that更常用, in order that更正式。so that引导的从句一般置于句末,而in order that引导的从句既可置于句首, 又可置于句末。
In order that the grass and flowers could bloom again,it was necessary that the rocks should be removed. She got up early so that she could catch the first bus.
(六)结果状语从句 结果状语从句一般由下列连词引导: so that, so…that, such…that。
He overslept, (so) that he was late for work. They got such a fright that they dropped the bag and ran away.
[提示] 1. so…that和such…that的区别。so后接形容词或副词, such后接名词。
It was so cold that we had to cancel the game. It's such a good chance that we mustn't miss it.
2. so that既可引导目的状语从句, 也可引导结果状语从句。so that引导目的状语从句时, 一般从句动词前会出现 can(could),may(might),shall(should),而so that引导的结果状语从句表示客观事实, 不会出现上述词语。 引导结果状语从句的so that前常有逗号, 表示强调。so that引导的目的状语可置于句首,而so that引导的结果状语从句只能置于句末。
He left early so that he could catch the train. 他早早动身, 以便能赶上车。(目的) He left early, so that he caught the train. 他早早动身, 赶上了火车。(结果)
(七)方式状语从句 引导方式状语从句的从属连词有as, as if(though), the way, how。 He made some changes as you had suggested. She was behaving as if (though) she hadn't grown up.
例句：
主语从句用作主语，如：：
That the earth is round is true． 地球为圆的是真实的。
宾语从句用作宾语。如：Do you know where he lives?
表语从句用作表语，如：
My opinion is that you should not go alone． 我的意见是你不应单独前往。
同位语从句用于解释说明前面的名词。如：
The fact that the earth is round is true． 地球是圆的的事实是真实的。（that从句用于解释说明the fact）
定语从句相当于一个形容词，用于修饰前面的名词。如：
The student who answered the question was John． 回答问题的学生是John．
状语从句相当于一个副词，如：
When it rains， I usually go to school by bus． 天下雨时，我通常坐公共汽车上学。（时间状语）
If he comes tomorrow， you will see him． 如果他明天来，你就可以看见他。（if 引导的条件状语从句，其结构为：if ＋状语从句，＋主句）。即主句是将来时，则从句要用一般现在时表示将来。
He returned home to learn his daughter had just been engaged．他回家后得知女儿刚刚订婚了。（结果状语，结果状语只是仅限于learn（得知），find（发现），see，hear，to be told（被告知），make（使得）等具有界限含义的动词。）
You must speak louder so that /in order that you can be heard by all． 你必须大声说话，才能让所有人听到你说话。（目的状语，可以由that， so that， in order that， lest， for fear that， in case等词引导。）
Since /As the weather is so bad， we have to delay our journey． 天气那么糟，旅行推迟了。 （原因状语从句，常用 because， since， as， for fear （ 恐怕 ）， seeing that （ 既然 ） ， now that （＝since）， considering that （ 考虑到 ） 等引导。）
Though/Though he was worn out， （still） he kept on working． 虽然他已经精疲力竭了，但仍然继续工作。 （让步状语从句，引导的连词主要有以下这些：though， although， as； even if， even though； whether…or…； no matter＋疑问词，疑问词－ever．）
Where I live there are plenty of trees． 我住的地方树很多。（地点状语从句，通常由where， wherever 引导。）
As water is to fish， so air is to man． 我们离不开空气，犹如鱼儿离不开水。（方式状语从句通常由as， （just） as…so…， as if， as though引导。）
