语法：连词 Link words连词是虚词，不能在句中单独担任成分，只起连接作用。
按其用法，连词可分为两大类：并列连词(Coordinate Conjunctions)和从属连词(Subordinate Conjunctions)。
一．并列连词：连接具有并列关系的词、短语或句子。
1. 并列关系：and, not only…but also…, both…and…, neither…nor…I used to live in Paris and London. Both Jane and Jim are interested in fishing.The weather here is neither too cold nor too hot.She is not only kind but also honest.2. 转折关系：but, yet, while(然而), when(然而，偏偏)The car is very old but it runs very fast.The problem was a little hard, yet I was able to work it out.The winter in Beijing is very cold while that of Kunming is warm.Why did you borrow the book when you had one?3. 选择关系：or, not…but…, either…or…,Would you like to live or would you like to stay?He is not a teacher but a writer. You can come either on Saturday or on Sunday.4. 因果关系：forIt must have rained last night, for the ground is wet now.The leaves of the trees are falling, for it’s already autumn.5. 区别（1）and和or1) 并列结构中，or通常用于否定句，and用于肯定句。
2) 但有时and 也可用于否定句。
请注意其不同特点：There is no air or water in the moon. There is no air and no water on the moon.在否定中并列结构用or 连接，但含有两个否定词的句子实际被看作是肯定结构，因此要用and。
典型例题---I don’t like chicken ___ fish. ---I don’t like chicken, ___ I like fish very much.A. and； andB. and； butC. or；butD. or；and答案C。
否定句中表并列用or, but 表转折。
判断改错：(错) We will die without air and water.(错) We can’t live without air or water.(对) We will die without air or water.(对) We can’t live without air and water.(2) 表示选择的并列结构1) or 意思为"否则"。
I must work hard, or I’ll fail in the exam.2) either…or 意思为"或者……或者……"。
注意谓语动词采用就近原则。
Either you or I am right.(3) 表示转折或对比1) but表示转折，while表示对比。
Some people love cats, while others hate them.典型例题--- Would you like to come to dinner tonight? --- I’d like to, ___ I’m too busy.A. andB. soC. asD. but答案D。
but与前面形成转折，符合语意。
而表并列的and，结果的so，原因的as都不符合句意。
2) not…but…意思为"不是……而是……" not 和but 后面的用词要遵循一致原则。
They were not the bones of an animal, but (the bones) of a human being.(4) 表原因关系1) for判断改错：(错) For he is ill, he is absent today.(对) He is absent today, for he is ill.for是并列连词，不能置于含两个并列分句的句子的句首，只能将其放在两个分句中间。
2) so, thereforeHe hurt his leg, so he couldn’t play in the game.注意：a. 两个并列连词不能连用，但therefore, then, yet.可以和并列连词连用。
You can watch TV, and /or you can go to bed.He hurt his leg, and so / and therefore he couldn’t play in the game.b. although… yet…，但although 不与 but连用。
(错) Although he was weak, but he tried his best to do the work..(对) Although he was weak, yet he tried his best to do the work. (5) 注意：not only… but also 关联两个分句时，一个分句因有否定词not 而必须倒装。
Not only does he like reading stories, but also he can even write some.neither…nor 意思为"既不……也不……"谓语动词采用就近原则，与nor后的词保持一致。
(6) 比较so和 such其规律由so与such的不同词性决定。
such 是形容词，修饰名词或名词词组，so 是副词，只能修饰形容词或副词。
so 还可与表示数量的形容词many，few，much，little连用，形成固定搭配。
so + adj. such + a(n) + n.so + adj. + a(n) + n. such + n. (pl.)so + adj. + n. (pl.) such +n. (pl.)so + adj. + n. [不可数] such +n. [不可数]so foolish such a foolso nice a flower such a nice flowerso many/ few flowers such nice flowersso much/little money. such rapid progressso many people such a lot of peopleso many 已成固定搭配，a lot of 虽相当于 many，但 a lot of 为名词性的，只能用such搭配。
so…that与such…that之间的转换即为so与such之间的转换。
二．从属连词：指在复合句中引导从句的连结词。
常见的从属连词有：引导时间状语从句的：after, before, when, as, while, since, until, till, as soon as引导原因状语从句的：because, since, as引导让步状语从句的：although, though, no matter（无论）, even if (though)引导条件状语从句的：if, unless, once, as (so) long as引导结果状语从句的：so, so that, so … that …, such … that …引导目的状语从句的：so, so that …, in orde r that …引导比较状语从句的：as … as …, not so (as), as, than引导方式状语从句的：as, as if …, as though引导地点状语从句的：where，wherever引导名词性从句（主语，宾语、表语或同位语从句）的连词主要有：that, whether, if三个。
其中that 和whether 间或还可以引起同位从句和状语从句。
（一）某些用法比较特殊的从属连词用法区别1、当while, when, as引导时间状语从句时的区别：①while引导的状语从句中动词必须是延续性。
谓语动词多为进行时，或状态动词的一般时。
while 的这些用法可用when代替，等于“at the time that”, “during the time that”。
例如：Please keep quiet while (when) others are studying；② when除可指一段时间外，还可用来指一点时间，等于“at the time”， when 引出的时间状语从句中的谓语动词可以是终止性的，也可以是延续性的。
因此主句和从句的谓语可以是一般时，进行时，或完成时。
例如：When I went into the lab, the teacher was doing an experiment.（不能用while）He often makes mistakes when heis speaking English.（when可换成while）③as常可与when，while通用，但强调“一边、一边”。
例如：As (when, while) I was walking down the street, I noticed a police car in front of number 37.④when引导的状语从句中的主语与主句主语一致，主、谓是“主语+系动词”结构时，这时主语和系动词可以省略。
例如：When (he was) young, he worked for a rich man.She’ll be here to give you help when (if it is) necessary.⑤when有时代替if，引导条件句，意为“如果”、“假如”，例如：I’ll come when (if) I’m free.2、before作连词一般表示时间，意为“在…之前”，但有些句子中这样译就显得别扭。
