Relative pronouns introduce a relative clause that gives more information about a noun or pronoun. They connect the clause to its antecedent, so the listener knows exactly which person, thing, place, or time you mean. In English, relative clauses can be defining meaning needed to identify the noun or non-defining extra information. Choosing the correct relative pronoun depends mainly on what you refer to and the role the pronoun plays inside the relative clause.

The core English relative pronouns are who, whom, whose, which, and that. Who and whom refer to people, which refers to things and sometimes animals, whose shows possession, and that can refer to people or things in defining relative clauses. There are also relative words like where, when, and why that work like relative pronouns for place, time, and reason.

Word/Phrase	🇨🇳 中文 单词/短语	Definition	🇨🇳 中文 定义	Example	🇨🇳 中文 示例
who	👤 who	Refers to people, often as the subject of the relative clause	👤 指人，通常作为关系从句的主语	The student who sits there is new.	🧩 坐在那里的学生是新生。
whom	👤 whom	Refers to people as the object in formal style	👤 在正式用法中指人作为宾语	The person whom I called did not answer.	🧩 我打电话给的那个人没有接。
whose	👤 whose	Shows possession for people, animals, or things	👤 表示人、动物或物的所有关系	I met a writer whose book won a prize.	🧩 我遇到了一位他写的书曾获奖的作家。
which	📦 which	Refers to things, and can introduce non-defining clauses	📦 指代事物，并且可以引入非限定性从句	The car which I bought is electric.	🧩 我买的那辆车是电动的。
that	🔗 that	Refers to people or things in defining clauses, common in speech	🔗 在限定性从句中指人或物，口语中常见	The movie that we watched was long.	🧩 我们看的那部电影很长。
where	📍 where	Refers to a place meaning in a relative clause	📍 在关系从句中指地点	This is the café where we met.	🧩 这是我们见面的咖啡馆。
when	⏰ when	Refers to time meaning in a relative clause	⏰ 在关系从句中指时间	I remember the day when we moved.	🧩 我记得我们搬家的那一天。
why	💡 why	Refers to reason meaning after reason	💡 表示原因，原因后的意思	That is the reason why she left.	🧩 那就是她离开的原因。

Defining relative clauses identify which specific person or thing you mean, so they are essential to the meaning of the sentence. They are not separated by commas. In defining clauses, that is very common, and who or which are also possible depending on the antecedent. If the relative pronoun is the object of the clause, it can often be omitted in defining clauses.

Non-defining relative clauses add extra information that is not needed to identify the noun. They are set off by commas, and in speech they are usually marked by a pause. In non-defining clauses, you generally use who, whom, whose, or which, and you do not use that. You also do not omit the relative pronoun in non-defining clauses.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
Use commas for non-defining relative clauses	🧷 在非限定性关系从句中使用逗号	My sister, who lives in Rome, is visiting.	🧩 我的姐姐，住在罗马，正在来访。
Do not use that in non-defining clauses	🚫 在非限定性从句中不要使用 that	The report, which was confidential, leaked.	🧩 那份报告，包含保密信息，泄露了。
Keep the relative pronoun in non-defining clauses	✅ 在非限定性从句中保留关系代词	The museum, which we visited yesterday, was crowded.	🧩 我们昨天参观的博物馆很挤。

The relative pronoun can function as the subject or the object inside the relative clause. If it is the subject, it cannot be omitted. If it is the object, it is often omitted in defining clauses, especially in speech and informal writing. Understanding the pronoun’s role helps you choose between who and whom and helps you decide whether omission is possible.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
Subject relative pronoun cannot be omitted	👤 主语关系代词不能省略	The woman who called left a message.	🧩 打电话的那位女士留下了留言。
Object relative pronoun can be omitted in defining clauses	🎯 宾语关系代词在限定性从句中可以省略	The woman I called left a message.	🧩 我打电话给的那位女士留下了留言。
Test: replace the pronoun with he she they or him her them in the clause	🧠 测试：在从句中用 he she they 或 him/her/them 替换代词	The man who helped us was kind. The man we thanked was kind.	🧩 帮助过我们的那位男士很友善。我们感谢的那位男士也很友善。

Who is used when the relative pronoun is the subject of the relative clause, while whom is used when it is the object, especially in formal style. In everyday English, whom is often replaced by who, except after a preposition in careful writing. In very informal speech, many speakers avoid whom entirely and restructure the sentence if needed.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
Use who as the subject in the relative clause	👤 在关系从句中用 who 作主语	The colleague who sits near me is helpful.	🧩 坐在我附近的那位同事很乐于助人。
Use whom as the object in formal style	🎯 在正式风格中用 whom 作宾语	The colleague whom I respect is retiring.	🧩 我尊敬的那位同事正在退休。
After a preposition, whom is common in formal writing	📌 在介词后，whom 在正式写作中很常见	The professor to whom I wrote replied.	🧩 我写信给的教授回信了。
In informal style, who often replaces whom	🗣 在非正式风格中，who 常常替代 whom	The person who I met yesterday was friendly.	🧩 我昨天遇到的那个人很友好。

Whose expresses possession and can refer to people, animals, and things. It links the antecedent to something that belongs to it, such as a body part, family member, property, or feature. Whose works in both defining and non-defining clauses and is often the most natural choice even when referring to things. It is followed by a noun phrase, not a complete clause.

That and which can both refer to things in defining relative clauses, but their distribution differs by style and punctuation. In American English, many writers prefer that for defining clauses and which for non-defining clauses. In British English, which is common in defining clauses as well, especially in more formal writing. Regardless of variety, which is the normal choice for non-defining clauses, and that is not used there.

Region	🇨🇳 中文 地区	Word	🇨🇳 中文 词语	Regional Definition	🇨🇳 中文 区域定义
🇺🇸American English	🇺🇸 美国英语	that	🔗 that	Commonly preferred for defining clauses about things	🔗 常用于定义性从句关于事物
🇺🇸American English	🇺🇸 美国英语	which	📦 which	Commonly preferred for non-defining clauses about things	📦 常用于非限定性从句关于事物
🇬🇧British English	🇬🇧 英国英语	which	📦 which	Often used in defining clauses as well as non-defining clauses	📦 常用于定义性从句以及非限定性从句
General	🌍 一般	that	🔗 that	Not used in non-defining clauses	🔗 在非限定性从句中不使用 that

With relative clauses, prepositions can appear at the end of the clause or before the relative pronoun. End-position prepositions are common and natural in conversation. Fronted prepositions are more formal and usually require whom for people and which for things. If the preposition is fronted, you cannot omit the relative pronoun.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
Common: preposition at the end	🗣 常见：介词放在句末	The chair that I sat on was broken.	🧩 我坐在上面的椅子坏了。
Formal: preposition before the relative pronoun	🎓 正式：介词放在关系代词前	The chair on which I sat was broken.	🧩 我坐在上面的那把椅子坏了。
Formal with people often uses whom	👤 正式与人相关时常用 whom	The client for whom we worked was satisfied.	🧩 我们为之工作的客户感到满意。
If the preposition is fronted, do not omit the pronoun	🚫 如果介词被前置，不要省略代词	The topic about which we spoke was sensitive.	🧩 我们讨论的那个话题很敏感。

Where, when, and why introduce relative clauses with meanings of place, time, and reason. They often replace patterns like in which, on which, or for which, and they are especially common in speech and general writing. They are most natural after nouns like place, day, time, and reason. In many cases, why can be omitted after reason without changing the meaning.

Rule	🇨🇳 中文 规则	Example	🇨🇳 中文 示例
Use where after place nouns	📍 在地点名词之后使用 where	This is the house where I grew up.	🧩 这是我长大的那所房子。
Use when after time nouns	⏰ 在时间名词之后使用 when	I will never forget the moment when she arrived.	🧩 我永远不会忘记她到达的那一刻。
Use why after reason, often optional	💡 在原因后使用 why，常是可选	That is the reason she left.	🧩 那就是她离开的原因。
More formal alternatives use preposition plus which	🔁 更正式的替代形式使用 介词加 which	This is the house in which I grew up.	🧩 这是我长大的那座房子。