摘要：对主句中的先行词（名词 / 代词）进行限定性修饰，不可省略，否则影响主句意思。

一、基本概念

定义：

对主句中的先行词（名词 / 代词）进行限定性修饰，不可省略，否则影响主句意思。

结构：

先行词 + 关系词 + 从句

例如：

The man who lives next door is a doctor.

（限定 “哪个男人”，去掉从句后句子不完整。）

（从句无逗号分隔）

例如：The girl who is singing is my sister.

二、限制性

限制性（无逗号）：

从句是主句不可缺少的部分

例：The man who lives next door is a doctor.

三、关系词分类及用法

1. 关系代词（作主 / 宾 / 定语）

2. 关系副词（作状语）

四、只能用 that 的特殊情况

1、先行词为不定代词：

something, anything, everything, nothing, all, few, little 等。

例：There’s nothing that I can do.

2、先行词被最高级 / 序数词修饰：

This is the best book that I’ve ever read.

3、先行词含人和物：

I saw people and things that were unforgettable.

4、先行词被 the only, the very, the same 等修饰：

He is the only person that can help you.

五、注意事项

1、关系词在从句中作宾语时可省略：

The movie (that) we watched last night was great.

主谓一致：

2、从句谓语动词与先行词保持一致。

The boy who is sitting there is my brother.

The books that are on the desk are mine.

3、关系词与介词的搭配：

介词可提前至关系代词前（介词 + which/whom）：

This is the room in which we lived.

也可后置，用关系副词或 “介词 + 关系代词”：

This is the room where we lived.= This is the room which we lived in.

来源：人尔个个