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
