批改作文时，我常看到这样的句子：
“I have a friend which is very funny.”
这里有两个问题：第一，描述人应该用who而不是which；第二，如果关系词在从句中作宾语，还可以省略。很多学生对定语从句关系词的选择规则模模糊糊——大概知道该用哪个，但一到写作就凭”感觉”选，结果经常出错。
📊 厦门灯塔威廉老师批改数据： 在我批改的300+篇英语作文中，约50%的学生在定语从句关系词选择上至少犯过一次错。最常见的问题是：用which指代人（占关系的30%）、that和which混用不分（占25%）、以及在非限制性定语从句中错误使用that（占20%）。
一、关系词选择三步法
只要按下面的步骤来，就不会选错：
第一步：判断先行词是人还是物？
- 人 → who / whom / that
- 物 → which / that
- 时间 → when
- 地点 → where
- 原因 → why（通常=for which）
第二步：判断关系词在从句中作什么成分？
- 主语 / 宾语 → who / which / that
- 宾语（且指人）→ whom（正式）或who/that/省略
- 所有格 → whose
- 时间状语 → when
- 地点状语 → where
第三步：判断是不是非限制性定语从句？
- 非限制（有逗号）→ 不用that
- 限制（无逗号）→ that/which都可以
二、详细对照表
| 先行词 | 作主语 | 作宾语 | 作所有格 | 作状语 |
|---|---|---|---|---|
| 人 | who/that | who/whom/that/省略 | whose | — |
| 物/动物 | which/that | which/that/省略 | whose/of which | — |
| 时间 | — | — | — | when/that/省略 |
| 地点 | — | — | — | where |
| 原因 | — | — | — | why/that/省略 |
三、几个容易混淆的考点
考点1：which和that什么时候可以互换？
限制性定语从句中： which = that，可以互换。
- The book which/that I bought yesterday is interesting. ✅
非限制性定语从句中（有逗号）： 只能用which，不能用that。
- ❌ My new book, that I bought yesterday, is great.
- ✅ My new book, which I bought yesterday, is great.
只能用that，不能用which的情况：
- 先行词被最高级修饰：This is the best movie that I’ve ever seen.
- 先行词被序数词修饰：He is the first person that came.
- 先行词包涵人和物：I remember the people and places that I visited.
- 先行词是all/everything/nothing等不定代词：There’s nothing that can stop me.
考点2：whose = 谁的 / 什么的
whose不只是”人的”，也可以指”物的”。
- ✅ The boy whose mother is a doctor is very smart.（人的）
- ✅ The house whose roof is red belongs to my uncle.（物的——= the roof of which）
很多考生以为whose只能指人，写”The house, the roof of which…”——没错，但太正式了。写作中用whose指物更简洁自然。
考点3：关系代词的省略规则
关系词在从句中作宾语时，可以省略。这是最容易被忽视的提分点——省略后句子更简洁。
- ❌ The man who/whom you met yesterday is my teacher.（正确但不简洁）
- ✅ The man you met yesterday is my teacher.（更自然）
- ❌ The book which I read is very good.（正确但啰嗦）
- ✅ The book I read is very good.（更简洁）
不能省略的场景：
- 关系词作主语时：The man who called you left a message.（who不能省）
- 非限制性定语从句中：Tom, who is my friend, came to see me.（who不能省）
四、写作中用定语从句的两个”最佳实践”
1. 两个简单句合为一个定语从句
Before（两个简单句）： I have a friend. She lives in Shanghai. She is a doctor.
After（一个定语从句）： I have a friend who lives in Shanghai and is a doctor.
这样写的效果：句子更紧凑，展示了句式变化能力——这正是中高考评分标准里的”句式多样性”加分点。
2. 用非限制性定语从句补充信息
Before（两个句子）： Beijing is the capital of China. It has a long history.
After（非限制性定语从句）： Beijing, which has a long history, is the capital of China.
非限制性定语从句不仅能提升句式复杂度，还能让你的写作逻辑更紧密——用一个句子表达”北京的历史+首都地位”两个信息。
五、常见错误对照表
| 错误 | 正确 | 说明 |
|---|---|---|
| I know a man which can help you. | I know a man who can help you. | 人用who，不用which |
| This is the house that I was born. | This is the house where I was born. | 地点用where |
| I remember the day which I met you. | I remember the day when I met you. | 时间用when |
| My teacher, that is very kind, helps me a lot. | My teacher, who is very kind, helps me a lot. | 非限制不用that |
| This is the most beautiful city which I’ve visited. | This is the most beautiful city that I’ve visited. | 最高级后用that |
定语从句不是”高级炫技”，而是一种提升写作效率的工具。用对了，你的文章会更紧凑、更有层次、更像”一个人写的”而不是”几个简单句拼起来的”。
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