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。
Stay where you are! 原地别动!
Though/Although she is rich, she’s not happy. 尽管她富有，但她并不幸福。
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. 并非每个人都诚实肯干，但汤姆是的。
We tried to persuade her to do it but failed. 我们尽力说服她去做，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. 飞机和它的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，而且记住了所读过的东西。
When we talk about the universe, we mean not only the earth, the sun, and the moon, but (also) all the other things too far away for us to see. 当我们谈到宇宙时，我们不但指地球、太阳和月亮，而且还指一切远得看不见的其他东西。
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)
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. 如：
误：He graduated from college in 2003, then he found a job.
正：He graduated from college in 2003, and then he found a job. / He graduated from college in 2003. 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：inaddition 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, none the less, 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 inIraqso far.
