定语从句是英语语法中的重要部分。定语从句用于修饰名词或代词，通常用于描述或限定名词或代词所指的人或物，从而使句子更加具体明确。下面将介绍定语从句的结构和用法。
定语从句的结构
定语从句一般由关系代词（who, whom, whose, which, that）引导，也有时由关系副词（where, when, why）引导。关系代词和关系副词在定语从句中作为从句的主语、宾语、定语或状语。
定语从句的结构如下：
主句 + 关系代词/关系副词 + 从句
例如：
- The book that I bought yesterday is very interesting.
- The woman who is sitting over there is my boss.
定语从句的用法
- 描述人或物
定语从句通常用于修饰名词或代词，从而更加具体地描述或限定人或物。例如：
- The car which is parked outside is mine.
- The teacher who teaches math is very strict.
- 确定身份
定语从句可以用于确定人或物的身份，从而避免歧义。例如：
- The man who is wearing a blue shirt is my brother.
- The company which produces high-quality products is very popular.
- 表示所属关系
定语从句可以用于表示所属关系，其中使用关系代词whose。例如：
- The girl whose bag was stolen called the police.
- The company whose profits increased last year is expanding its business.
- 修饰整个句子
定语从句可以用于修饰整个句子，从而起到补充说明的作用。例如：
- When we arrived at the airport, which was very busy, we had to wait in a long line.
- I finally found my keys, which I had lost last week.
定语从句是英语语法中不可或缺的一部分，掌握定语从句的结构和用法对于提高英语水平非常重要。希望大家通过本文的介绍，能够更好地理解和应用定语从句。
