英语学习中，从句是构建复杂句子的基石。掌握不同类型的从句及其用法，对于提升阅读理解、写作能力至关重要。本文将对英语从句的各类知识点进行归纳，力求全面清晰。

一、名词性从句

名词性从句在句子中起名词的作用，可以充当主语、宾语、表语、同位语。

1. 主语从句：位于句首，整个从句充当句子的主语。常用的引导词有 that, whether/if, wh-词 (who, what, which, when, where, why, how)。

That he passed the exam surprised everyone. (他通过考试让所有人惊讶。)

Whether/If she will come is still uncertain. (她是否会来还不确定。)

What he said is not important. (他说什么不重要。)

2. 宾语从句：位于及物动词或介词之后，充当宾语。引导词与主语从句类似。

I know that she is a doctor. (我知道她是一名医生。)

He asked me whether/if I had seen the movie. (他问我是否看过这部电影。)

She doesn't know what she wants. (她不知道她想要什么。)

I am concerned about what might happen. (我担心会发生什么事。)

3. 表语从句：位于系动词之后，构成复合句的表语。常用的引导词也是 that, whether/if, wh-词。

The problem is that we don't have enough time. (问题是我们没有足够的时间。)

The question is whether/if we should accept the offer. (问题是我们是否应该接受这个提议。)

My suggestion is what we discussed yesterday. (我的建议是我们昨天讨论的内容。)

4. 同位语从句：对名词进行解释说明，通常位于抽象名词如 fact, idea, news, suggestion, hope 等之后。常用 that 引导。

The fact that he lied to me is unforgivable. (他对我撒谎这个事实是不可原谅的。)

The news that the company is going bankrupt spread quickly. (公司即将破产的消息迅速传开。)

二、定语从句

定语从句修饰名词或代词，相当于一个形容词，也称为关系从句。引导词包括关系代词 (who, whom, whose, which, that) 和关系副词 (when, where, why)。

1. 关系代词：

who: 指代人，在从句中作主语。 The man who is talking to her is my brother. (正在和她说话的那个人是我的兄弟。)

whom: 指代人，在从句中作宾语。 The woman whom I saw yesterday is a famous singer. (我昨天见到的那位女士是一位著名的歌手。)

whose: 指代人或物，表示所属关系。 The girl whose car was stolen reported it to the police. (车被偷的女孩向警察报了案。)

which: 指代物，在从句中作主语或宾语。 The book which I borrowed from the library is very interesting. (我从图书馆借来的那本书很有趣。)

that: 可以指代人或物，在非限制性定语从句中不能使用。The house that I live in is very old. (我住的房子很旧。)

2. 关系副词：

when: 指代时间。 I will never forget the day when I met you. (我永远不会忘记我遇见你的那一天。)

where: 指代地点。 This is the restaurant where we had our first date. (这是我们第一次约会的餐厅。)

why: 指代原因。 I don't know the reason why he left. (我不知道他离开的原因。)

3. 限制性定语从句和非限制性定语从句：

限制性定语从句对先行词起限制作用，是句子的必要成分，不用逗号隔开。

非限制性定语从句对先行词起补充说明作用，不是句子的必要成分，用逗号隔开。 My brother, who is a teacher, lives in Beijing. (我的哥哥，他是一位老师，住在北京。)

三、状语从句

状语从句在句子中作状语，修饰动词、形容词、副词或整个句子。根据其表达的意义，可分为以下几种：

1. 时间状语从句：常用引导词有 when, while, as, before, after, until/till, as soon as, since, whenever, no sooner...than, hardly/scarcely...when.

When I saw him, he was reading a book. (当我看到他的时候，他正在看书。)

I will call you as soon as I arrive. (我一到达就会给你打电话。)

2. 地点状语从句：常用引导词 where, wherever.

Where there is a will, there is a way. (有志者，事竟成。)

You can sit wherever you like. (你可以随便坐。)

3. 原因状语从句：常用引导词 because, as, since, for.

I stayed at home because it was raining. (我待在家里是因为下雨了。)

Since you are busy, I will do it myself. (既然你很忙，我自己来做吧。)

4. 条件状语从句：常用引导词 if, unless, as long as, provided/providing (that), on condition that.

If it rains, we will stay at home. (如果下雨，我们就待在家里。)

You can go as long as you promise to be careful. (只要你答应小心，你就可以去。)

5. 目的状语从句：常用引导词 so that, in order that, that.

He studied hard so that he could pass the exam. (他努力学习，以便能通过考试。)

6. 结果状语从句：常用引导词 so...that, such...that.

He was so tired that he fell asleep immediately. (他太累了，所以立刻睡着了。)

It was such a good movie that I watched it twice. (这部电影太好了，所以我看了两遍。)

7. 让步状语从句：常用引导词 although/though, even though/even if, as, while, no matter + wh-词, however, whoever, whatever, wherever, whenever.

Although it was raining, we went for a walk. (尽管下雨，我们还是去散步了。)

No matter what happens, I will always be there for you. (无论发生什么，我都会在你身边。)

8. 方式状语从句：常用引导词 as, as if/as though.

Do as I told you. (按照我告诉你的做。)

He acted as if he knew everything. (他表现得好像他什么都知道。)

9. 比较状语从句：常用引导词 as...as, than.

He is as tall as his father. (他和他父亲一样高。)

She is younger than I am. (她比我年轻。)

理解和掌握这些从句的用法，并能够在实际运用中灵活运用，是提高英语水平的关键。在学习过程中，多做练习，多分析句子结构，才能真正掌握从句这一重要的语法知识点。