在英语语法的学习过程中，定语从句是一个重要的知识点。它能够帮助我们更准确地表达事物之间的关系，使句子更加丰富和精确。今天我们就来一起复习一下定语从句的基本概念及其应用。

什么是定语从句？

定语从句是用来修饰名词或代词的从句，通常放在被修饰的名词或代词之后，起着补充说明的作用。简单来说，定语从句就像是一把钥匙，帮助我们打开一个名词或代词背后隐藏的信息。

例如：

- The book that I bought yesterday is very interesting.

在这个句子中，“that I bought yesterday”就是定语从句，用来描述“book”。

定语从句的结构

定语从句由关系代词或关系副词引导。根据引导词的不同，定语从句可以分为两大类：

1. 关系代词引导的定语从句

常见的关系代词有：who, whom, whose, which, that等。这些词既可以指代人也可以指代物，具体使用取决于先行词（即被修饰的名词）的性质。

- Who/Whom: 指代人，在从句中作主语或宾语。

- He is the man who works hard every day.

- Whose: 表示所属关系。

- This is the house whose windows face south.

- Which: 指代事物。

- The car which broke down was repaired yesterday.

- That: 可以指代人或事物。

- She is the girl that I met at the party.

2. 关系副词引导的定语从句

关系副词包括where, when, why等。它们分别表示地点、时间以及原因。

- Where: 表示地点。

- This is the place where we first met.

- When: 表示时间。

- Do you remember the day when it happened?

- Why: 表示原因。

- The reason why he failed is clear.

注意事项

1. 在非限制性定语从句中，不能使用关系代词that。

- 正确：He has a brother, who is a doctor.

- 错误：He has a brother, that is a doctor.

2. 当先行词是all, anything, something, nothing等不定代词时，通常使用关系代词that。

- All that glitters is not gold.

3. 如果先行词既有人又有物，则只能用关系代词that。

- The teacher and the book that were mentioned in the report are both excellent.

练习题

1. The girl _______ you talked to just now is my sister.

2. The book _______ you lent me is very interesting.

3. The reason _______ he gave for being late was unacceptable.

4. This is the factory _______ we visited last year.

通过以上内容的复习，相信大家对定语从句已经有了更深的理解。希望大家能够在实际运用中灵活掌握这一语法点，让自己的英语表达更加地道流畅！