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。例如
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。
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。例：
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。例如：
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。例如：
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。例如：
He is better educated than his pother. 他比他兄弟受的教育好。
He is as well educated as his pother. 他和他兄弟受的教育一样好。
He is not as/so well educated as his pother. 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。例如：
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。
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医.学.全.在.线www.lindalemus.com，两个分句或主从复合句之间用逗号连接。
(三)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. 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.或者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：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。如：
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.
