一、概说
连词是一种虚词，用于连接单词、短语、从句或句子，在句子中不单独用作句子成分。连词按其性质可分为并列连词和从属连词。并列连词用于连接并列的单词、短语、从句或句子，如and,but, or, for等；从属连词主要引出名词性从句(主语从句、宾语从句、表语从句等)和状语从句(时间状语从句、条件状语从句、目的状语从句等)，引出名词性从句的连词如that,whether等，引出状语从句的连词如when, because,since, if 等。
二、并列连词的用法
1. 表示转折关系的并列连词。这类连词主要有 but, yet 等。
如：
Someone borrowed my pen, but I don't remember who.
有人借了我的钢笔，但我不记得是谁了。
He said he was our friend, yet he wouldn't help us.
他说他是我们的朋友，但却不肯帮助我们。
2. 表示因果关系的并列连词。
这类连词主要有 for, so 等。
如：
The child had a bad cough, so his mother took him to the doctor.
这孩子咳得很利害，所以他妈妈带他去看医生。
You are supposed to get rid of carelessness, for it often leads to serious errors.
你们一定要克服粗枝大叶，因为粗枝大叶常常引起严重的错误。
注意：for表示结果通常不能放句首，也不能单独使用。
3. 表示并列关系的并列连词。
这类连词主要有 and , or , either…or , neither…nor , not only…but (also) ,both…and , as well as 等。
如：
He didn't go and she didn't go either.
他没去，她也没去。
The weather is mild today; it is neither hot nor cold.
今天天气很温暖，不冷也不热。
Both New York and London have traffic problems.
纽约和伦敦都存在交通问题。
It is important for you as well as for me.
这对你和对我都很重要。
People who are either under age or over age may not join the army.
年龄不到或者超龄的人都不得参军。
三、从属连词的用法
1. 引导时间状语从句的从属连词
(1) 表示“当…时候”或“每当”的时间连词。主要的 when,while, as, whenever。
如：
Don't talk while you're eating.
吃饭时不要说话。
Vegetables are best when they are fresh.
蔬菜新鲜时最好吃。
He came just as I was leaving.
我正要走时他来了。
(2) 表示“在……之前(或之后)”的时间连词。主要的有before, after。
如：
Try to finish your work before you leave.
离开前设法把工作做完。
After we have finished tea, we will sit on the grass.
喝完茶之后我们将坐在草地上。
(3) 表示“自从”或“直到”的时间连词。主要的有since, until, till。
如：
She's been playing tennis since she was eight.
她从八岁起就打网球了。
Hold on until I fetch help.
坚持一下，等我找人来帮忙。
Never trouble trouble till trouble troubles you.
(谚)不要无事惹事。
(4) 表示“一……就”的时间连词。主要的有：
as soon as, the moment, the minute, thesecond, theinstant, immediately, directly, instantly, once, no sooner…than,hardly…when等。
如：
I'll let you know as soon as I hear from her.
我一接她的信就通知你。
The moment I have finished I'll give you a call.
我一干完就给你打电话。
I came immediately I heard the news.
我一听到这个消息，马上就来了。
Once you begin you must continue.
你一旦开始, 便不可停下来。
(5) 表示“上次”、“下次”、“每次”等的时间连词。主要的有every time(每次)，eachtime(每次)，(the) nexttime(下次)，any time(随时)，(the) last time(上次)，thefirst time(第一次)。
如：
I'll tell him about it (the) next time I see him.
我下一次见到他时，我就把这个情况告诉他。
We lose a few skin cells every time we wash our hands.
每当我们洗手的时候，我们都要损失一些皮肤细胞。
You can call me any time you want to.
你随时都可以给我打电话。
注意：every time, each time, any time前不用冠词，(the) next time, (the) last time中的冠词可以省略，而the first time中的冠词通常不能省略。
2. 引导条件状语从句的从属连词。
这类连词主要有if,unless, as [so] longas, incase 等。
如：
Do you mind if I open the window?
我开窗你不介意吧?
Don't come unless I telephone.
除非我打电话，否则你别来。
As long as you're happy, it doesn't matter what youdo.
只要你高兴，你做什么都没关系。
In case it rains they will stay at home.
万一下雨，他们就呆在家里。
注意：在条件状语从句中，通常要用一般现在时表示将来意义，而不能直接使用将来时态。不过，有时表示条件的 if之后可能用 will，但那不是将来时态, 而是表示意愿或委婉的请求(will为情态动词)。
如：
If you will sit down for a few moments, I'll tell the manager you're here.
请稍坐, 我这就通知经理说您来了。
3. 引导目的状语从句的从属连词。
主要的有 inorderthat, sothat, incase, forfear等。
如：
He raised his voice so that everyone could hear.
他提高了嗓音，以便每个人都能听见。
Take your umbrella (just) in case it rains.
带上雨伞，以防下雨。
She repeated the instructions slowly in order that he should understand.
她把那些指示慢慢重复了一遍好让他听明白。
4. 引导结果状语从句的从属连词。
主要的有so that, so…that, such…that等。
如：
I went to the lecture early so that I got a good seat.
我去听演讲去得很早, 所以找个好座位。
I had so many falls that I was black and blue all over.
我摔了许多跤，以致于全身都是青一块紫一块的。
He shut the window with such force that the glass broke.
他关窗子用力很大, 结果玻璃震破了。
5. 引导原因状语从句的从属连词。
主要的有because, as, since, seeing (that), now (that), considering(that) 等。
如：
He distrusted me because I was new.
他不信任我，因为我是新来的。
As you are sorry, I'll forgive you.
既然你悔悟了，我就原谅你。
Since we've no money, we can't buy it.
由于我们没钱，我们无法购买它。
Seeing that he's ill he's unlikely to come.
因为他病了，他大概不会来了。
Now that she has apologized, I am content.
既然她已经道了歉, 我也就满意了。
6. 引导让步状语从句的从属连词。
主要的有although,though, eventhough, evenif, while, however,whatever,whoever, whenever, wherever等。
如：
Although they are twins, they look entirely different.
他们虽是孪生, 但是相貌却完全不同。
I like her even though she can be annoying.
尽管她有时很恼人, 但我还是喜欢她。
You won't move that stone, however strong you are.
不管你力气多大, 也休想搬动那块石头。
Whatever we have achieved, we owe to your support.
我们取得的一切成就都归功于你们的支持。
Whoever you are, you can't pass this way.
不管你是谁，你都不能从这里通过。
Whenever I see him I speak to him.
每当我见到他，我都和他讲话。
7. 引导方式状语从句的从属连词。
主要的有as, as if, as though, the way等。
如：
Why didn't you catch the last bus as I told you to?
你怎么不听我的话赶乘末班公共汽车呢?
He bent the iron bar as if it had been made of rubber.
他将铁棍折弯，仿佛那是用橡皮做成的。
Nobody else loves you the way(=as) I do.
没有人像我这样爱你。
8. 引导地点状语从句的从属连词。
主要的有where, wherever, everywhere, anywhere等。
如：
The church was built where there had once been a Roman temple.
这座教堂盖在一座罗马寺庙的旧址。
I'll take you anywhere you like.
你想到哪儿我就带你到哪儿。
Everywhere I go, I find the same thing.
不管我走到哪里，我都发现同样情况。
9. 引导比较状语从句的从属连词。
主要的有than和as…as。
如：
She was now happier than she had ever been.
现在她比过去任何时候都快活。
I glanced at my watch. It was earlier than I thought.
我看了看表，时间比我想像的早。
He doesn't work as hard as she does.
他工作不像她那样努力。
10. 引起名词从句的从属连词。
主要有that, whether, if 等，它们用于引导主语从句、表语从句、宾语从句和同位语从句。其中that 不仅没不充当句子成分，而且没有词义，在句子中只起连接作用；而 if,whether 虽不充当句子成分，但有词义，即表示“是否”。
如：
He replied that he was going by train.
他回答说他将坐火车去。
I wonder if it's large enough.
我不知道它是否够大。
I worry about whether I hurt her feelings.
我为是否伤了她的感情而担心。
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