【英语中的从句】在英语语法中，从句是句子中具有主语和谓语的结构，它不能单独成句，必须依附于主句。从句通常由引导词（如 that, which, who, when, where 等）引导，用来补充说明主句的内容或表达更复杂的意思。掌握从句的用法对于提高英语写作和阅读理解能力至关重要。
一、从句分类总结
| 从句类型 | 引导词 | 功能 | 示例 |
| 名词性从句 | that, whether, if, what, who, how, when, where, why | 在句中作主语、宾语、表语或同位语 | I don’t know what he said. |
| 定语从句 | who, whom, whose, which, that, when, where, why | 修饰名词或代词 | The book that is on the table is mine. |
| 状语从句 | because, although, if, when, since, unless, as, while, so...that, such...that | 表示时间、原因、条件、目的等 | If it rains, we will stay home. |
| 同位语从句 | that | 对前面的名词进行解释说明 | The fact that he failed surprised everyone. |
二、常见从句详解
1. 名词性从句
- 主语从句：在句中充当主语。
What he did surprised me.
- 宾语从句：在句中充当动词或介词的宾语。
I believe that he is honest.
- 表语从句：在系动词后作表语。
The problem is whether we can finish it on time.
- 同位语从句：对前面的名词进行具体说明。
The news that he passed the exam is true.
2. 定语从句
- 限制性定语从句：对先行词起限定作用，不可省略。
The man who is talking to Mary is my teacher.
- 非限制性定语从句：对先行词进行补充说明，用逗号隔开。
My brother, who lives in Beijing, is coming to visit us.
3. 状语从句
- 时间状语从句：表示动作发生的时间。
When she arrived, we were having dinner.
- 原因状语从句：表示动作发生的原因。
Because it was raining, we stayed indoors.
- 条件状语从句：表示假设情况下的结果。
If you study hard, you will pass the exam.
- 目的状语从句：表示动作的目的。
He left early so that he could catch the train.
4. 同位语从句
- 通常由 that 引导，对前面的抽象名词进行解释。
The idea that we should start early is reasonable.
三、注意事项
- 从句的语序应为陈述语序，而不是疑问语序。
✅ I asked what he wanted.
❌ I asked what did he want.
- 某些引导词在从句中可省略，但需注意语境是否允许。
✅ I know (that) he is tired.
- 从句的位置通常在主句之后，但在某些情况下可以前置。
✅ That he didn’t come surprised everyone.
通过掌握这些从句的类型和用法，可以帮助学习者更准确地理解和运用英语句子结构，提升语言表达的多样性和准确性。
