连词分类：
1、并列连词：是指连接对等的词、词组和句子，而不是连接主句与从句的连词，如：and, both…and, neither…nor, not only…but also, as well as, but, however, while(而),
still, yet, or, either…or, otherwise, so, for, therefore, thus, accordingly, consequently, hence, then,等。
2．从属连词：指连接主句与从句的连词，如：that, whether, if, before, after, as , as soon as, once, since, ever since, till, until, when, whenever,while, because, since, now that(既然), so…that, such…that, so that, in order that, as if,
as though, though, although, even though, even ifno matter who/whoever/…，unless, as/so long as, in case(以防), lest(惟恐), provided, providing, （如果）supposed,
supposing,（假使） 等。二、代词的分类1. 关系代词a) 有who, whom, whose, as, that和which, 是用来引起定语从句的。who, whom代表人，在从句中作主语时用who, 作宾语时用whom： There is a girl who wants to see you. 有一个姑娘想见你。
He is the man whom you asked to see. 他就是你要求见的人。 whose表示“他(她)的”，在从句中作定语： Do you know the girl whose painting won the first prize? 你认识那个作品赢得头奖的姑娘吗？
这些关系代词，一方面引起定语从句，修饰前面的那个名词，一方面在从句中担任一个成分。(who作主语，whom作宾语，whose作定语。) b) which代表事物，在从句中可以作主语或宾语：还可以代替整个句子；
He told us a story which was very interesting. 他给我们讲了一个非常有趣的故事。 This is the book which I bought. 这就是我买的那本书。
that也可代表事物，在从句中作宾语： Have you got everything that you need? 你需要的东西都有吗？ 在从句中作宾语的关系代词，有时可以省略：That’s the book I bought. 这就是我买的书。
He is always late for school, which makes his teacher very angry.c) 关系代词as : As is known to all, the earth is round. The earth is round, as is known to all.
关于关系代词详见定语从句。2. 连接代词指引起从句的疑问代词，可用用来引起主语从句(a)、宾语从句(b)和表语从句(c)： a. Who is to be sent there hasn’t been decided. 派谁去还没决定。 b. I don’t know who did it. 我不知道这是谁干的。
c. The question is what we should do next. 问题是下一步我们该怎么办。 what可有特殊意义，表示the thing which(…的东西)，可作主语(a)、宾语(b)和表语(c)： a. What you need is more practice. 你需要的是更多练习。
b. Show me what you bought. 把你买的东西给我看看。 c. That’s what I heard. 这是我听到的情况。 这可以称作关系代词型的what。希望能帮到您，谢谢采纳!