Grammar Rule in 30 Seconds
Defining clauses identify exactly who/what you mean; non-defining clauses just add extra details using commas.
- Defining: No commas, 'that' is okay, essential for meaning. Example: 'The car that I bought is red.'
- Non-Defining: Use commas, 'that' is NOT okay, extra info only. Example: 'My car, which is red, is fast.'
- Omission: In defining clauses, you can drop 'who/which/that' if it's the object. Example: 'The book (that) I read.'
Overview
The cat that is white is so moody（那只白色的猫脾气真古怪），他使用的是限定性定语从句 (defining relative clause)。为什么？因为如果没有 that is white 这部分，你就不知道他在说哪只猫！现在，想象一下他只有一只猫。如果他说 My cat, which is white, is so moody（我的猫——它是白色的——脾气真古怪），那就是非限定性定语从句 (non-defining relative clause)。猫是白色这个事实只是一个额外的细节。你已经知道是哪只猫了——就是他唯一的两只猫。How This Grammar Works
The movie that we watched last night was awesome（我们昨晚看的那部电影太棒了），that we watched last night 这个从句就是激光笔。它准确地告诉你我指的是哪部电影。如果我把它拿走，只说 The movie was awesome，你可能会说：“哪部电影，哥们？我们连着看了六个小时 Netflix。”Inception, which we watched last night, was awesome（《盗梦空间》——我们昨晚看的——太棒了），你已经知道这部电影是《盗梦空间》了。我们昨晚看它这个事实只是一个额外的小信息。如果我撕掉那个便利贴，句子 Inception was awesome 仍然完全说得通。My girlfriend who lives in London is coming to visit 暗示你在其他城市还有其他女朋友（危险举动！），而 My girlfriend, who lives in London, is coming to visit 只是告诉我们你唯一的亲爱的住在哪里。
Formation Pattern
the laptop 笔记本电脑，my boss 我的老板）。
who 或 that（限定性）或仅使用 who（非限定性）。
which 或 that（限定性）或仅使用 which（非限定性）。
that 有点宅。它只住在限定性从句里。它永远不会去非限定性从句。
I、you、we），你通常可以完全删除它（The phone [that] I bought）。在非限定性从句中，代词是强制性的。它是永远不会离开派对的 VIP。
When To Use It
I want the burger that has no onions（我要那个不加洋葱的汉堡），那个从句是 100% 必要的。没有它，你只会得到一个随机的汉堡，你的晚餐就毁了。当你在区分一组相似事物中的某一个时，使用它。它非常适合写评论：The hotel that we stayed at was trash（我们住的那家酒店很烂），或者抱怨科技：The update that I downloaded broke my phone（我下载的更新把手机搞坏了）。Sarah, who has ten years of experience in marketing, joined our team.（萨拉——她有十年的市场营销经验——加入了我们的团队。）你已经知道她是萨拉了。她的经验只是她很优秀的一个原因。当名词已经是唯一的——比如一个人的名字、一个特定的地方（Paris）或一个独特的关系（my mother）时，使用这些。如果你在八卦某个名人，你会说：Taylor Swift, who is currently on tour, just released a new album.（泰勒·斯威夫特——她目前正在巡演中——刚发行了新专辑。）我们知道泰勒是谁；巡演信息只是一个“顺便一提”。
Common Mistakes
- 逗号闹剧：在非限定性从句中忘记逗号是第一大错误。写成
My dad who is a doctor lives in Berlin意味着你有多个爸爸，而你正在识别那个当医生的。除非你处在一个非常现代的家庭动态中，否则你可能需要那些逗号：My dad, who is a doctor, lives in Berlin. - “That”陷阱：在非限定性从句中使用
that。你不能说：✗ Paris, that I love, is beautiful.这听起来像是黑客帝国的错误。改用which：✓ Paris, which I love, is beautiful. - “Who”混淆：有时人们对人使用
which。千万别这么做！✗ The guy which lives next door是一个大错误。应该是✓ The guy who lives next door。 - 双重主语：在从句后添加额外的代词。
✗ The car that I bought it is fast.你不需要这个it！关系代词that已经承担了宾语的工作。保持简洁：✓ The car that I bought is fast. - 省略成癖：试图删除非限定性从句中的代词。
✗ My brother, lives in Tokyo, is a chef.你需要那个who来填补空缺：✓ My brother, who lives in Tokyo, is a chef.
Contrast With Similar Patterns
My friend, a professional gamer, is rich。这与 My friend, who is a professional gamer, is rich 非常相似。区别在于定语从句使用动词（is），而同位语只使用名词短语。两者都用于“额外信息”，而且都喜欢逗号。The girl sitting over there，而不是说 The girl who is sitting over there。这是一种更高级、更“酷”的表达方式，让你听起来非常有母语感。这仅适用于关系代词作主语的限定性从句。I know what you did（我知道你做了什么）。定语从句修饰名词，比如 I know the person who did it（我认识做这件事的人）。一个是关于“什么”，另一个是关于“谁”。这就像知道一个秘密和认识那个泄密的人之间的区别。Quick FAQ
which 吗？The car which I bought 完全没问题，尽管 that 在日常口语中更常见。只是永远不要在非限定性从句中使用 that。who 或 that 可以吗？The man [who] I saw 没问题。The man who saw me 不行——你需要 who 因为它是主语。John，我们就知道是约翰。之后的任何信息都会自动被视为“额外”信息，因此需要逗号。My sister who lives in Spain。不加逗号！这告诉听者你是在两个姐姐中选择一个。神奇吧？Relative Pronoun Selection
| Function | For People | For Things | For Places/Time |
|---|---|---|---|
|
Subject
|
who / that
|
which / that
|
N/A
|
|
Object
|
who / whom / that / (ø)
|
which / that / (ø)
|
where / when
|
|
Possessive
|
whose
|
whose / of which
|
N/A
|
Pronoun Omission (Defining Only)
| Full Form | Short Form (Omitted) | Condition |
|---|---|---|
|
The man who I met
|
The man I met
|
Pronoun is the Object
|
|
The book that you read
|
The book you read
|
Pronoun is the Object
|
|
The man who lives here
|
NOT POSSIBLE
|
Pronoun is the Subject
|
Meanings
Relative clauses provide more information about a noun. Defining clauses limit the noun to a specific one, while non-defining clauses provide supplementary details about a noun already identified.
Defining (Restrictive)
Tells us which specific person or thing we are talking about. Without it, the sentence is incomplete or unclear.
“The students who studied hard passed the exam.”
“I'm looking for the keys that I left on the table.”
Non-Defining (Non-Restrictive)
Adds extra information about a noun we already know. The sentence still makes sense if you remove this clause.
“My brother, who lives in New York, is a chef.”
“The Eiffel Tower, which was built in 1889, is in Paris.”
Object Pronoun Omission
In defining clauses, if the relative pronoun is the object of the verb, it can be deleted.
“The movie (that) we watched was boring.”
“The person (who) I called didn't answer.”
Reference Table
| 特征 | 限定性从句 (Defining) | 非限定性从句 (Non-Defining) |
|---|---|---|
|
主要目的
|
识别/锁定名词
|
提供额外补充信息
|
|
是否用逗号
|
从不使用逗号
|
必须使用逗号
|
|
能否用 'that'?
|
可以（非常常见）
|
绝对不行！
|
|
能否省略关系词?
|
可以（作宾语时）
|
绝对不行
|
|
例子
|
The car that I like...
|
My car, which I like,...
|
|
去掉后的影响
|
句子意思变得不明确
|
句子意思依然完整清晰
|
正式程度
The colleague with whom I collaborated on the project is absent. (Workplace)
The colleague who I worked with on the project is away. (Workplace)
The guy I worked with is out. (Workplace)
My project partner's ghosting today. (Workplace)
定语从句：身份测试
限定性 (核心信息)
- 无逗号 Identification
- 使用 'That' Casual/Daily
非限定性 (额外信息)
- 有逗号 Bonus Detail
- 禁用 'That' Strict Rule
限定性 vs. 非限定性
加不加逗号？
如果去掉这个从句，句子意思还明确吗？
名词是特定的名字或唯一的事物吗（如 'Paris'）？
代词使用限制
两者通用
- • Who (指人)
- • Which (指物)
- • Whose
- • Where
仅限限定性
- • That
- • 省略 (零代词)
按水平分级的例句
The boy who is happy is my brother.
The boy who is happy is my brother.
I have a dog that is big.
I have a dog that is big.
This is the book that I want.
This is the book that I want.
The girl who lives here is nice.
The girl who lives here is nice.
The car which he bought is blue.
The car which he bought is blue.
The man (who) I saw yesterday was tall.
The man (who) I saw yesterday was tall.
I like the city where I was born.
I like the city where I was born.
She is the teacher who helps me.
She is the teacher who helps me.
My sister, who lives in Rome, is a lawyer.
My sister, who lives in Rome, is a lawyer.
The laptop that I use for work is broken.
The laptop that I use for work is broken.
London, which is the capital of the UK, is huge.
London, which is the capital of the UK, is huge.
The man whose car was stolen is very angry.
The man whose car was stolen is very angry.
The company, which was founded in 1920, is closing.
The company, which was founded in 1920, is closing.
He failed his driving test, which was a surprise.
He failed his driving test, which was a surprise.
The candidate for whom I voted didn't win.
The candidate for whom I voted didn't win.
Is that the reason why you were late?
Is that the reason why you were late?
The building, the roof of which was damaged, is old.
The building, the roof of which was damaged, is old.
Anyone wishing to leave early may do so.
Anyone wishing to leave early may do so.
The method by which they achieved this is unknown.
The method by which they achieved this is unknown.
The town, where many artists live, is very vibrant.
The town, where many artists live, is very vibrant.
The project, the success of which remains to be seen, is costly.
The project, the success of which remains to be seen, is costly.
He was late, as is often the case with him.
He was late, as is often the case with him.
Whosoever finds the key shall be rewarded.
Whosoever finds the key shall be rewarded.
The situation, albeit difficult, is not hopeless.
The situation, albeit difficult, is not hopeless.
容易混淆
Learners often use them interchangeably in all contexts.
Learners aren't sure when to use the object form 'whom'.
Both describe nouns but use different structures.
常见错误
The man which lives here.
The man who lives here.
I like the book what you gave me.
I like the book that you gave me.
The girl she lives next door is nice.
The girl who lives next door is nice.
I saw the man who he is a doctor.
I saw the man who is a doctor.
The house that I live is small.
The house where I live is small.
This is the man who's car is red.
This is the man whose car is red.
The movie who I saw was good.
The movie that I saw was good.
My mother, that is 50, is a nurse.
My mother, who is 50, is a nurse.
Paris which is in France is beautiful.
Paris, which is in France, is beautiful.
The man, who I met him, was nice.
The man, who I met, was nice.
The car, that's engine is broken, is mine.
The car, whose engine is broken, is mine.
句型
The ___ who ___ is ___.
___, which is ___, is ___.
The ___ (that) I ___ was ___.
The person whose ___ is ___.
Real World Usage
My bestie, who is literally the cutest, just graduated!
I am looking for a role that allows me to use my coding skills.
The suspect, who was arrested late last night, is being questioned.
Did you find the keys I lost?
The theory, which was first proposed in 1990, remains controversial.
Take the train that goes toward the city center.
手指指向大法
The car that I want is expensive.
逗号后面别用 That
My cat, which is sleeping, is cute.
正式程度有别
The movie that we watched was great.
Smart Tips
Always use a non-defining clause with commas. Proper nouns are already specific, so any extra info is just 'extra'.
Use 'whom' after prepositions like 'to', 'with', or 'for'.
Check if there is another subject immediately after it. If there is, you can usually delete it.
Use ', which' at the end of the sentence.
发音
The Comma Pause
In non-defining clauses, there is a slight drop in pitch and a brief pause where the commas are.
Relative Pronoun Reduction
In fast speech, 'that' is often pronounced with a schwa /ðət/.
Non-defining Parenthetical
My car, (which is red), is fast.
The pitch goes down for the clause and back up for the main verb.
记住它
记忆技巧
Defining is 'Determining' (no commas needed), Non-defining is 'Needless' (needs commas).
视觉联想
Imagine a defining clause as a wedding ring—it's essential and stays on the finger. Imagine a non-defining clause as a bracelet—it's extra, and you can take it off (the commas are the clasps).
Rhyme
If it's extra, use a comma. If it's needed, save the drama.
Story
A detective is looking for 'the man who stole the diamond' (Defining). Once he catches him, he says, 'This man, who is wearing a red hat, is the thief' (Non-defining).
Word Web
挑战
Look at 5 objects in your room. Write one defining and one non-defining sentence for each.
文化笔记
British speakers are slightly more likely to use 'which' in defining clauses than American speakers, who strictly prefer 'that'.
Using 'whom' is almost exclusively reserved for formal writing or very formal speeches. Using it in casual conversation can sound pretentious.
In some dialects, 'that' is used for people more frequently than 'who' in informal speech.
Relative pronouns in English evolved from demonstrative and interrogative pronouns in Old English ('se', 'seo', 'þæt').
对话开场白
Tell me about a person who has influenced your life.
Describe your hometown, which I've never visited.
What's a movie that you've seen more than three times?
Think of a famous person whom you admire.
日记主题
常见错误
Test Yourself
选择正确的句子：
Tokyo, ___ is the capital of Japan, is a huge city.
Find and fix the mistake:
Mr. Smith that is my teacher is very kind.
Score: /3
练习题
8 exercisesMy brother, ___ lives in Spain, is visiting next week.
The woman ___ car was stolen called the police.
Find and fix the mistake:
The laptop, that I bought yesterday, is very fast.
I have a friend. He speaks five languages.
Match types
The cake that I ate was delicious.
The man who lives here is nice.
This is the park ___ we first met.
Score: /8
Practice Bank
10 exercisesThe phone ___ I bought yesterday is broken.
哪一个是正确的？
Paris / is / which / beautiful / I / visited / , / ,
The girl which lives next door is nice.
Kucing yang sedang tidur itu milikku. (那只正在睡觉的猫是我的。)
匹配项：
My mother, ___ is 60, still runs marathons.
哪个句子识别了一个特定的事物？
The man who is standing there is my uncle.
The company, ___ headquarters are in London, is hiring.
Score: /10
常见问题 (8)
Use a comma if the information is 'extra'. If the sentence still makes sense without it, add commas. If the info is needed to know which noun you mean, no commas.
In defining clauses, yes (e.g., 'The man that I saw'). In non-defining clauses, no—you must use 'who'.
'Who' is for subjects (the person doing the action). 'Whom' is for objects (the person receiving the action). 'Whom' is mostly used in formal writing.
No. You can only drop it in defining clauses when it is the object of the sentence (e.g., 'The book I read'). You cannot drop it if it is the subject (e.g., 'The book that is on the table').
In defining clauses, 'which' can sound slightly more formal than 'that', especially in British English. In non-defining clauses, 'which' is the only option for things.
Yes! It is perfectly natural to say 'The car whose engine is broken' instead of the more clunky 'The car the engine of which is broken'.
This is a standard rule of English grammar. 'That' is considered a restrictive pronoun, meaning its job is to limit or define. Non-defining clauses don't limit, so 'that' doesn't fit.
It might change the meaning! 'My brother who is a doctor' implies you have multiple brothers and you're talking about the doctor one. 'My brother, who is a doctor,' implies you have one brother and he happens to be a doctor.
Scaffolded Practice
1
2
3
4
Mastery Progress
Needs Practice
Improving
Strong
Mastered
In Other Languages
que / quien / el cual
English distinguishes between 'that' and 'which' based on commas; Spanish uses 'que' for both.
qui / que / lequel
French relative pronouns are determined by grammatical function (subject/object), not by the 'essentialness' of the info.
der / die / das
German requires commas for every relative clause, whereas English only uses them for non-defining ones.
Pre-nominal modifiers
Japanese uses word order (clause + noun) instead of pronouns (noun + who/which).
al-ladhi (الذي)
Arabic requires a pronoun like 'him' or 'it' inside the clause (e.g., 'the man who I saw him').
de (的)
Chinese places the description before the noun, while English places it after.
Learning Path
Prerequisites
Learn These First
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