1、连词的含义：连词是一种虚词，不承担句子的任何成分，是一种连接词与词、短语与短语、或引导从句的词。
2、连词的分类：连词分为并列连接词和从属连接词两种。
①、并列连接词连接并列的词、短语、从句或句子。常见有：and(和),but(但是),or(或者,否则),nor(也不), so(所以), however(然而,无论如何),for(因为),still(可是),as well as(也), both...and...(...和...), not only ...but also...(不但…而且…), either… or…(或…或…),neither… nor…(既不…也不…)等。
补充：(1)表并列关系的and, both…and, not only…but also, neither…nor等。
(2)表选择关系的or, either…or等。(3)表转折关系的but, while等。(4)表因果关系的for, so等。
②、从属连接词用于引导从句,常见的有：
when(当…时候), while(正当…时候), after(在…之后), before(在…之前), since(自从), until(直到), although/though(虽然), if(假如), as(如…一样；由于), as …as…(和…一样), as far as(就…而言), as long as(只要), as soon as(一…就…), even if(即使), because(因为), unless (除非), than(比…), whether (是否…), in order that…(为了), so…that…(如此…以致), so that…(以便), now that…(现在既然), by the time…(到…时候), every time…(每当), as if…(好像),no matter when(或whenever)(无论何时),no matter where(或wherever)(无论在哪里)等。
补充：(1)引导时间状语从句的after, before, when, while, as, until, till, since, as soon as等。
(2)引导条件状语从句的if, unless等。 (3)引导原因状语从句的because, as, since等。
(4)引导目的状语从句的so that, in order that等。 (5)引导让步状语从句的though, although, even if等。
(6)引导结果状语从句的so that, so…that, such…that等。 (7)引导比较状语从句的than, as…as等。
(8)引导名词从句的that, if , whether等。
［辨析］ ：
(1)Hurry up, or you’ll miss the train. (快点，否则你会错过火车) Hurry up, and you’ll catch the train. (快点，你会赶上火车的)
(2) not only ...but also...(不但…而且…), either… or…(或…或…),neither… nor…(既不…也不…)，这三个连词词组都可连接两个并列成分。当它们连接两个并列主语时，谓语动词要随相邻的主语变化。例:
Either you or he is wrong. /Neither he nor his children like fish.不但他不喜欢而且他的孩子也不喜欢鱼。
Not only the teacher but also the students want to buy the book.不但老师而且学生想买这本书。
(3) because、as、since、for的用法：
①because(因为)，引导原因状语从句。表示原因的语气最强,常表示必然的因果关系,从句常放主句后面；回答why的问句只能用because. eg：He is not at school today because he is seriously ill.
②as(因为)，引导原因状语从句。表示一般的因果关系,语气比because弱,说明比较明显的原因,它引导的从句放在句首，句尾都可以。As all of you have got here, now, let’s go to the zoo.
③since(既然)，引导原因状语从句表示对方已经知道、无需加以说明的原因或事实。
I will ask Lin Tao to go with me since you are very busy. 更多资料QQ378459309制作：
④for(因为)是并列连词, 引导并列句。语气较弱,用来补充说明理由或提供一种解释，只能放在主句后面。
We must be off now for the match starts at 7：00.
★(4)if、whether的区别：
相同点：表示“是否”时,if和whether同义,引导宾语从句, I don’t know if/whether he will arrive on time.
不同点：①whether提出两种选择时要用whether，不用if. 如Let me know whether he can come or not.
②在不定式前或介词后只用whether. eg: Please ask him whether to go there with a raincoat or not.
I have not settled the question of whether I will go home.
③whether与or not连用时, if不可以
④whether引导主语从句或表语从句,
Whether it is a fine day next Sunday is still a question. / The question is whether he will go.
⑤If “是否”意思不能放句首，whether可以. eg: Whether she is at home, I can not say.
⑥而if还可以表示“如果”,引导条件状语从句,(主句与从句遵循主将从现的原则)。
I will ring you up if he arrives on time.
(5)while、when、as的用法区别：
①while常表示一个较长的动作,它引导的从句动作与主句的动作是同时发生的、是平行的；
②when可表较短的动作也可表较长的动作,主句和从句的动作可同时发生也可先后发生；
③as与上两词同义,可替换while和when,表示主句和从句的动作同时发生,常译为“一边…一边……”，主句从句均为短动作时也常用as。
Please do not trouble me while I am writing my homework. / I’ll go home when I have finished my job. They were running quickly across the road when they heard the sound of a truck coming.
As we walked in the dark street, we sang songs and talked loudly.
(6)till/until与not…till/until的区别：
till/until (肯定)主句常是一个延续性的动作, not…till/until（否定）主句常是一个短暂性动作。(都是引导时间状语从句，符合主将从现的原则)
如：①I will stay here and watch the baby until you return.（我会呆在这里看着娃娃直到你回来）(stay这个动作是一个延续性动作，一直进行到你return)
②I won’t go to bed until my father comes back.
（直到我父亲回来我才会去睡觉，go是一个短动作）
③ I didn’t go to bed until my father came back.（直到我父亲回来我才去睡觉，
从句动作应该在主句动作前发生，也就是先父亲先回来,我才去睡觉）
④ He didn’t tell me anything_______ he left. (青岛试题)
A. until B. before C. after D. Since
另外till与until基本可以互换,但是在句首时只能用until,不能用till.
如：Until the last minute of the match we kept playing.
Not until he had finished his work did he go home.（直到做完工作他才回家）（倒装句）
(7)though与although的区别：
①两个词都表示“虽然”,均不可以与but同时使用,但在句中可加still或yet连用。
He passed the exams although illness prevented him from going to classes.
②although“尽管、虽然”仅作连词,比较正式,一般可换为though；
③though“虽然、尽管、即使”,可与even连用(even though= ),表示“即使、纵然”,
She won’t leave the TV set, even though her husband is waiting for her for the supper.
④though还可作副词时意思是“然而、不过”,不能放在句首。
It was a quiet party. I had a good time, though.（这是个不热闹的聚会尽管如此我还是玩得很开心）
(8)prefer to…rather than…与prefer…to…的区别：
①prefer to do sth rather than do sth宁愿做某事，而不愿做某事情
I prefer to learn English rather than learn Japanese.
②prefer…to…都是用动名词或名词。
I prefer English to Japanese. / I prefer staying at home to going swimming.
9） so…that中的so是个副词，其后只能跟形容词或副词，而such...that中的such是个形容词，后接名词或名词短语。例如：I’m so tired that I can’t walk any farther.我很累，因此不想再走了。
It was such a hot day that he went swimming.如此热的天气，以至于他去游泳。
2) 如果在名词之前有many, much, little, few时，用so,不用such。例如：
He has so little education that he is unable to get a job.他受到得教育很少以致于他找不到工作。