Mastering B2 Relative Clauses: Defining vs. Non-Defining — B2 English grammar lesson by Langcom

Mastering B2 Relative Clauses: Defining vs. Non-Defining

劳尔-马吉尼亚

Langcom 创始人 | 剑桥考试和SIELE考试考官

9 月 20, 2026

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Relative clauses add information to a noun, but it’s crucial to understand if that information is essential (defining) or extra (non-defining), as this changes punctuation and pronoun choice. Defining relative clauses give necessary details about a noun. Without this information, the sentence’s meaning is unclear. They do not use commas. For example, The student who studies hard passes the exam. Here, who studies hard tells us *which* specific student. Non-defining relative clauses provide additional, non-essential information. This information can be removed without changing the main meaning of the sentence. They are always separated by commas. For instance, My sister, who lives in London, is a doctor. The information who lives in London is extra; I still know who my sister is. Incorrect comma use can completely change the meaning of your sentence, leading to misunderstandings. Mastering these rules is key for clear and accurate communication at B2 level.

What Are Relative Clauses?

Relative clauses are parts of a sentence that give more information about a noun or pronoun. They connect two ideas into one smoother sentence.

They usually start with a relative pronoun like who, which, that, whose, or a relative adverb like where, when, why.

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Defining vs. Non-Defining: What’s the Difference?

There are two main types of relative clauses: defining and non-defining.

  • Defining Relative Clauses: These clauses provide essential information. The sentence’s meaning changes or becomes unclear if you remove them. They answer the question “Which one?” or “What kind?”
  • Non-Defining Relative Clauses: These clauses give extra, non-essential information. You can remove them, and the main meaning of the sentence will stay the same. They add interesting details.

Why Are Commas Important in Relative Clauses?

Punctuation is the key difference between defining and non-defining clauses.

  • Defining clauses do NOT use commas. They are directly connected to the noun they describe.
  • Non-defining clauses ALWAYS use commas to separate them from the rest of the sentence. Think of the commas like parentheses, showing that the information is extra.

Using commas incorrectly can change the meaning of your sentence completely. For example:

  • The sports facilities which are not in regular use will be sold. (Only the unused facilities will be sold.)
  • The sports facilities, which are not in regular use, will be sold. (All sports facilities will be sold, and by the way, none are in regular use.)

Which Relative Pronouns Can You Use?

The choice of relative pronoun depends on whether the clause is defining or non-defining, and if you are talking about people or things.

In Defining Relative Clauses:

  • For people: 使用 whothat.
  • For things: 使用 whichthat.

In Non-Defining Relative Clauses:

  • For people: 使用 who.
  • For things: 使用 which.
  • Important: You CANNOT use that in non-defining relative clauses.

Can You Omit Relative Pronouns?

Sometimes you can leave out the relative pronoun, but only in specific situations.

  • When to omit: You can omit the relative pronoun (like who, which, that) in a defining relative clause if it is the object of the verb in the relative clause.
  • When NOT to omit: You must include the relative pronoun if it is the subject of the verb in the relative clause. You also cannot omit pronouns in non-defining clauses.

What About ‘Where’, ‘When’, and ‘Why’?

Besides pronouns, you can also use relative adverbs to introduce clauses.

  • Where refers to a place.
  • When refers to a time.
  • Why refers to a reason.

In defining relative clauses, you can sometimes omit whenwhy.

Summary of Relative Clause Rules
功能 Defining Relative Clauses Non-Defining Relative Clauses
Information Essential (cannot be removed) Extra (can be removed)
Punctuation No commas Always use commas
For People who, that who
For Things which, that which
Can use that? Yes No
Can omit pronoun? Yes (if object of verb) No

示例

  • The girl who is studying to become a vet is called Sarah.
  • Sarah, who is 20, is studying to become a vet.
  • The boy who is playing is the county champion.
  • The teacher that I met is the Head of Maths.
  • Colours which can be worn are black, navy and grey.
  • The book that I recommend costs £8.50.
  • Ted, who plays the violin, is living above a music shop.
  • The new brand of shampoo, which is selling well, contains only natural ingredients.
  • The hotel where we stayed had a beautiful garden.
  • Christmas is the time (when) many people start thinking about their next holiday.
  • That’s the reason (why) I left early.

练习

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西班牙语母语者常犯的错误

1. Using that in non-defining clauses:

Many learners incorrectly use that in non-defining clauses. Remember, that is only for defining clauses.

  • 错误: My car, that is red, is very fast.
  • 正确: My car, which is red, is very fast.

2. Missing commas in non-defining clauses:

Forgetting commas is a common error that can change your sentence’s meaning.

  • 错误: My brother who lives in Canada is visiting. (This implies you have more than one brother, and you are specifying which one.)
  • 正确: My brother, who lives in Canada, is visiting. (This implies you have one brother, and you are adding extra information about him.)

3. Adding commas to defining clauses:

Defining clauses should not have commas.

  • 错误: The book, that I read, was excellent.
  • 正确: The book that I read was excellent.

常见问题

限定性从句和非限定性从句的主要区别是什么?

The main difference is whether the information is essential or extra. Defining clauses give essential information and use no commas. Non-defining clauses give extra information and are always separated by commas.

Can I always use ‘that’ instead of ‘who’ or ‘which’?

No. You can use that 而不是 whowhich only in defining relative clauses. You cannot use that in non-defining relative clauses.

When can I leave out the relative pronoun?

You can leave out the relative pronoun (like who, which, that) only in defining relative clauses when it is the object of the verb in the relative clause. If it’s the subject, you must keep it.

How are relative clauses tested in the B2 First exam?

Relative clauses often appear in the B2 First (FCE) Use of English paper. You might find them in Part 2 (Open Cloze), where you need to provide the correct relative pronoun, or in Part 4 (Key Word Transformation), where you may need to rewrite a sentence using a relative clause correctly, paying attention to punctuation.

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关于作者:劳尔·马吉尼亚

劳尔·马吉尼亚是Langcom教育协会的主任,该协会是位于 美国. 凭借在语言教育和国际认证领域十余年的经验,他已帮助来自25个国家的数千名学生、教师和教育机构考取了剑桥英语证书以及IELTS、TOEFL和Michigan英语证书。.

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