连接词是英语中的一个重要组成部分，它们连接英语的句子和段落，使文章流畅自然，使英语句子与句子之间，段落与段落之间的关系一目了然。英语中连接词分为两大类：连词性连接词(即连词)和副词性连接词。
一、连词性连接词(连词)
连词用来连接词与词、短语与短语或句子与句子。连词不能单独作句子成分，也没有词形变化。连词分为并列连词和从属连词两种。
(一)并列连词
并列连词用来连接句子中担任相同成分的词、短语或分句。常见的有七个单词和四个短语：and, but, or, for(因为), nor, so, yet; both…and…, not only….but also…., either…or…., neither…nor
1. and用来连接词、短语或分句，表示并列或对称关系：
The man put on his coat and hat, and went out of the office. 那个人穿上外衣、戴上帽子，走出了办公室。
A car and a dictionary are both useful. 汽车和字典都有用处。
I went home and John stayed there. 我回家了，而约翰呆在那里。
2. but连接两个含义不同甚至相反的词、短语或分句，表示转折：
Not everybody is honest and hardworking, but Tom is. 并非每个人都跟汤姆一样诚实肯干。
We tried to persuade her to do it but failed. 我们尝试去说服她，但没有成功。
3. or表示两者居其一，表示选择：
Which VCD player is better, this one or that one? 哪个VCD更好，这个还是那个?
Are you hungry or not? 你饿了没有?
4 .for(因为)只能放在表示结过的分句后面，引导表示原因的分句：
I must be going, for it’s getting dark. 我必须走了，因为天黑了。
He didn’t go there, for he was ill. 他没到那儿去，因为他病了。
5. both…and…只能用来连接两个并列的词或短语，不能连接句子：
His plan is both easy and practical. 他的计划既容易又实用。
Zhang Yimou is a famous director both at home and abroad. 张艺谋是一位在国内外都著名的导演。
Both this plane and its engines are made in China. 这架飞机的机身和发动机都是中国制造的。
6. not only…but also…不但能连接词和短语，而且还能连接分句,also 有时省略(注意not only 位于句首时，主语和谓语需要倒装)：
He is not only an actor but also a writer. 他不仅是演员，而且是作家。
He not only read it but also remembered what he had read. 他不但读过，而且记住了所有读过的东西。
Not only did he say it but (also) he did it. 他不但说了，而且做了。(倒装)
Not only do the nurses want a pay rise, but also they want reduced hours. 护士们不但要求加工资，而且还要求缩短工时。(倒装)
7. either…or…表示选择，“或者…或者…”、“不是….就是…”的意思(注意either…or…整个结构作主语时句子中的动词通常要和邻近的主语相一致)：
Either you are wrong, or I am. 不是你错了，就是我错了。
Either you or he is going to get the job. 不是你就是他将获得这份工作。
Can I borrow either your car or your bike? 我可以借用你的汽车或者自行车吗?
If you’re late, you should make an apology to the host either immediately or later. 如果迟到了，你应该立即或事后向主人道歉。
8. neither…nor…表示“既不….又不…”的意思(注意neither…nor…整个结构作主语时，句子中的谓语动词通常要和邻近的主语一致)：
Neither the students nor I am ready yet. 学生们和我都还没有准备好。
He worked neither for fame nor for money. 他干工作既不图名又不图利。
The girl could neither speak nor write the language. 这个女孩既不会说也不会写那种语言。
9. so(因此)，引导表示结过的分句，原因分句在前(与for相反)：
It’s getting dark, so I must be going. 天黑了，因此我得走了。
I had a headache, so I went to bed early last night. 我头痛，于是昨晚很早就睡了。
10. yet (然而)，有时和and 一起用，表示吃惊、表示转折，相当于but at the same time, however, nevertheless:
She’s a funny girl, yet you can’t help liking her. 她是个疯疯癫癫的女孩，然而你却禁不住喜欢她。
He worked hard, yet he failed. 他很努力，然而却失败了。
It’s strange, yet it’s true. 这事有点怪，却是真的。
It is only a little shop and yet it always has such lovely decorations. 那只是个小店，却总是有漂亮的装饰。
(二)从属连词：引导从句
1. 连词that, if, whether，连接代词what, which, who, whom, whose以及连接副词how, when, why, where可用来引导名词从句，充当主语、表语、宾语等。非正式文体中的宾语从句常省略that：
I think (that) he’ll be back in an hour. 我认为他一小时后就会回来。
Who they are doesn’t matter much. 他们是谁没什么大关系。
Can you tell me where he is? 你能告诉我他在哪儿吗?
He asked me if/whether I knew John. 他问我是否认识约翰。
此外，that, which, who, whom, whose, when, why, where等还可以引导定语从句。
2. 连词when, while, before, after, till/until, since, as soon as等引导时间状语从句：
She said hello to me when she saw me. 她看到我的时候，和我打了招呼。
I’ll wait here until you come back. 我将在这里等你回来。
3. 连词if, unless引导条件状语从句;because, as, since引导原因状语从句：
I’ll help her if she asks me to. 如果她要求我，我就帮助她。
I won’t help her unless she asks me to. 除非她要求我，否则我不会帮她。
He didn’t come because he was ill. 因为他病了，所以没来。
As he hasn’t appeared yet, we shall start without him. 既然他还没有出现，我们就先开始吧。
Since everybody is here, let’s begin. 既然大家都到了，咱们就开始吧。
4. 连词in order than, so that引导目的状语从句;so…that…引导结果状语从句：
I locked the door in order that we might continue our discussions undisturbed. (=I locked the door in order to continue our discussions undisturbed.) 我把门锁上了，以便我们可以继续讨论而不受打扰。
The car ran so fast that I couldn’t see who was in it. 汽车跑得那么快，我没看清谁坐在里面。
5. 连词than, as…as…, not as/so…as…用来引导比较状语从句：
He is better educated than his brother. 他比他兄弟受的教育好。
He is as well educated as his brother. 他和他兄弟受的教育一样好。
He is not as/so well educated as his brother. 他没有他兄弟受的教育好。
6. 连词although, though 引导让步状语从句;where, wherever 引导地点状语从句：
I’ll go wherever you go. 不管你去哪儿，我就去那儿。
Though/Although she is rich, she’s not happy. 尽管她富有，但她并不幸福。
Stay where you are! 原地别动!
一般来说，连词性质的连接词连接两个分句或引导一个从句，两个分句或主从复合句之间用逗号连接。
二、副词性连接词
副词性质的连接词不能象连词一样分句或主从复合句之间用逗号连接。也就是说它们不能连接两个分句或引导从句。它们引导的句子与前面的句子之间要用分号或句号，而它们与引导的句子之间往往用逗号。副词性质的连接词在写作中常常使用，主要分为以下几类：
1. 表示顺序的，如first, in the first place, then, finally, in the end等等，尤其要注意then：
误：He graduated from college in 2003, then he found a job.
正：He graduated from college in 2003. Then he found a job.(=He graduated from college in 2003, and then he found a job.)
2. 表示递进关系的，如in addition, what is more, furthermore, moreover等。注意in addition 与in addition to 的区别：in addition 是副词性质;而in addition to 是介词性质，后面必须接宾语
3. 表示转折关系的，如 however, nevertheless, nonetheless, on the contrary, in contrast, 等等。要注意不要把however 当成连词：
误：In 2003, the United States launched the war on Iraq on account of Iraq possessing weapons of mass destruction (WMD), however, no WMD has been found in Iraq so far.
正：In 2003, the United States launched the war on Iraq on account of Iraq possessing weapons of mass destruction (WMD). However, no WMD has been found in Iraq so far.
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