连词是一种在句子与句子之间，短语之间以及名词等其他词语之间起连接作用的虚词，它不能单独作句子的成份。按其意义可分为并列连词和从属连词两大类。 并 列连词连接的双方是对等的。常有的并列连词有and, both…and, either…or, neither…nor， not only…but also, as well as等。但如果连接的两部分意义不趋向一致，意义有转折的并列连词有：but, however, while (而)，only (只不过)。还有表示选择关系的并列连词，如：or, or else, otherwise… 再有的是连接双方，互为因果，或表示前因后果的连词有：for, so, therefore (因此)，then等。 从属连词在初中范围内常常用来连接名词性从句，如：that, if, whether, 其次用来连接状语从句。其中有原因状语从句，常用的连接词有：when while, as, since, before, after, once, as soon as, until, till 连接条件状语的连词有：if, unless, as long as 等，而原因状语的连接词有because, since, as, now that (既然)。目的、结果、方式、比较、地点等状语从句的连接词有：so that, so…that, such…that, as…as, than, where… 它们在句子与文章中几乎无处不见。 具体用法见下表。
种类 功用 例句
并列连词 连接具有并列关系的 词 He knows neither English nor French.
短语 Are you going by bus or on foot?
分句 Mary was a good girl, but she had one shortcoming.
从属连词 引导： 状语从句 I***9;ll do it as you told me.
You will be late unless you hurry.
连接代词和连接副词 主语从句 What he said proved true.
When we***9;ll start has not been decided yet.
表语从句 This is why he didn***9;t come yesterday.
That is where he lives.
宾语从句 The man asked me which I liked best.?
I can***9;t understand why she is so late.
关系代词和关系副词 定语从句 Nicotine is a drug that gets one into the habit of smoking.?
He came last night when I was out.
[误] Both my parents are not here. They went to the concert just now.
[正] Neither of my parents is here. They went to the concert just now.
[析] 在英语中both一般用于肯定句中，如用于否定句中，其意义也不同于汉语，如：Both of us are not right. 在英语中应被理解为"我们俩不都对。"而Neither of us is right。 才能被理解为"我们俩无一正确"。
[误] He or his parents has some tickets for the film.
[正] He or his parents have some tickets for the film.
[析] 由or 连接两主语时，谓语动词应与相临近的那一个主语保持一致。
[误] You should study hard, and you won***9;t pass the exam.
[正] You should study hard, or you won***9;t pass the exam.
[析] or作为连词，这里的意思为"否则"。又如：Hurry up, or you***9;ll be late for school.
[误] Though he is poor, but he is ready to help others.
[正] Though he is poor, he is ready to help others.
[误] Because he didn***9;t study hard, so he didn***9;t pass the exam.
[正] He didn***9;t pass the exam because he didn***9;t study hard.
[析] because 与 so在英文中两者不能并用的，只能在句中用其一。
[误] He was such excited that he could not speak.
[正] He was so excited that he could not speak.
[析] so与such的用法可以分为四种情况，①用于单数可数名词之前，其格式是such+不定冠词+形容词+单数可数名词，如：It is such a beautiful book that every child likes it. 也可以用so, 其格式是so+形容词+不定冠词+单数可数名词，如：It was so beautiful a book that every child likes it. ②在不可数名词前或可数名词复数前这时只能用such, 如：It is such good weather that we want to swim. 又如：They are such good students that they can pass the exam easily. ③在few, little， much, many 这4个字前只能用so而不能用such, 如：I have so much money that I can buy everything I want. ④当that前只有形容词或副词时，这时只能用so, 如：She is so beautiful that every one likes her. He ran so fast that I couldn***9;t keep up with him.
[误] He got up earlier this morning so as to that he could catch the first bus.
[正] He got up earlier this morning so as to catch the first bus.
[正] He got up so earlier that he could catch the first bus.
[析] so…that与so that的用法有相同之处，那就是其后接从句，而so as to 其后要接不定式，即动词原形。这样的词组还有：in order to。
[误] I want to buy same stamp that you have.
[正] I want to buy the same stamp as you have.
[析] the same…as (that)这是个固定用法，在same前的定冠词是不能少的。而the same…that意为"我要的就是那一个"。而the same…as为"要的是和……一样的东西"。
[误] Before I do not give you the answer, I***9;ll ask you some questions.
[正] Before I give you the answer, I***9;ll ask you some questions.