If you’ve ever written a sentence like “The book that I borrowed was fascinating” or “She is the teacher who changed my life,” you’ve already used a relative pronoun — probably without even thinking about it. Relative pronouns are small words that do a surprisingly big job in English. They connect ideas, add detail, and help you build richer, more fluent sentences. But what exactly is a relative pronoun, and how does it work? This guide breaks it all down in a clear, practical way.
What Is a Relative Pronoun? (Simple Definition)
A relative pronoun is a word that introduces a relative clause — a group of words that gives more information about a noun or pronoun mentioned earlier in the sentence.
The noun or pronoun being described is called the antecedent. The relative pronoun connects the relative clause back to that antecedent, acting like a bridge between two ideas.
Think of it this way:
“I met a scientist. The scientist discovered a new planet.”
Without a relative pronoun, you need two separate sentences. With one, you can combine them elegantly:
“I met a scientist who discovered a new planet.”
Here, who is the relative pronoun. It refers back to “scientist” (the antecedent) and introduces the clause “who discovered a new planet.”
The Five Main Relative Pronouns in English
English has five core relative pronouns. Each one is used in slightly different contexts depending on the antecedent and the pronoun’s role in the clause.
| Relative Pronoun | Used For | Role in Clause |
|---|---|---|
| Who | People | Subject |
| Whom | People | Object |
| Whose | People, animals, things (possession) | Possessive |
| Which | Animals, things, ideas | Subject or Object |
| That | People, animals, things | Subject or Object |
Let’s explore each one in detail.
1. Who
Who refers to people and functions as the subject of the relative clause — meaning it performs the action of the verb in that clause.
- The doctor who treated me was very kind.
- Students who study regularly tend to perform better.
- My neighbor, who is a chef, made us dinner.
In the first example, “who” refers to “the doctor,” and “the doctor” is the one doing the treating — so “who” acts as the subject of its clause.
2. Whom
Whom also refers to people, but it functions as the object of the verb or preposition in the relative clause.
- The professor whom I admire most just published a book.
- The candidate whom they selected was highly experienced.
- She is the person to whom I owe the most gratitude.
A helpful trick: if you can substitute him or her in the clause, use whom. If you can substitute he or she, use who.
“I admire him” → “the professor whom I admire” ✓
In casual spoken English, “who” is often used in place of “whom,” and this is widely accepted. However, “whom” remains the grammatically correct choice in formal writing.
3. Whose
Whose shows possession or belonging. It can refer to people, animals, or even things when ownership or association is implied.
- The artist whose painting won the award smiled broadly.
- We stayed at a hotel whose rooms were beautifully designed.
- A child whose parents work abroad often feels lonely.
Notice that “whose” replaces a possessive form — in the first example, it replaces “the artist’s” in the implied sentence “the artist’s painting won the award.”
4. Which
Which refers to animals, things, and ideas — not people. It can function as the subject or object of the relative clause.
- The report, which took three weeks to write, was finally submitted.
- He drives a car which runs on electricity.
- The new policy, which was introduced last year, has been effective.
“Which” is also commonly used in non-defining relative clauses (more on this below), where it’s set off by commas.
5. That
That is the most flexible relative pronoun. It can refer to people, animals, or things and can serve as either subject or object.
- The film that won the Oscar was released last year.
- The dog that lives next door barks all night.
- Everything that she said was true.
However, “that” is generally used only in defining (restrictive) relative clauses and is not typically used after a comma in non-defining clauses.
Defining vs. Non-Defining Relative Clauses
This is one of the most important distinctions in understanding how relative pronouns work. The type of clause determines your punctuation — and sometimes your choice of pronoun.
Defining (Restrictive) Relative Clauses
A defining relative clause provides essential information about the antecedent. Without it, the sentence would lose its specific meaning or become unclear. These clauses are not separated by commas.
- The student who answered first won a prize.
- I want to buy the house that has a red door.
- The book which I recommended is out of stock.
If you removed the relative clause from the first example, you’d just have “The student won a prize” — which student? The clause is essential.
Non-Defining (Non-Restrictive) Relative Clauses
A non-defining relative clause adds extra, bonus information about the antecedent. The sentence still makes complete sense without it. These clauses are separated by commas.
- My sister, who lives in Paris, is a fashion designer.
- The Eiffel Tower, which was built in 1889, attracts millions of visitors.
- Professor Lee, whose research is groundbreaking, will speak tonight.
Notice: “That” is not used in non-defining relative clauses. You would not say: “My sister, that lives in Paris…” — this is grammatically incorrect.
When Can You Omit the Relative Pronoun?
In English, you can sometimes leave out the relative pronoun entirely — but only when it functions as the object of the relative clause, not the subject.
Compare these two sentences:
- The movie that I watched last night was brilliant. → The movie I watched last night was brilliant. ✓
- The man who called you left a message. → ~~The man called you left a message.~~ ✗
In the first example, “that” is the object of “watched” (I watched it), so it can be dropped. In the second, “who” is the subject of “called,” so it cannot be omitted.
This is known as a contact clause or zero relative clause, and it’s extremely common in spoken and informal English.
Common Mistakes with Relative Pronouns
Even advanced English learners trip up on relative pronouns. Here are the most frequent errors — and how to avoid them.
Mistake 1: Using “which” for people
- ❌ The teacher which taught me math was strict.
- ✅ The teacher who taught me math was strict.
Mistake 2: Using “that” in non-defining clauses
- ❌ London, that is the capital of England, is a vibrant city.
- ✅ London, which is the capital of England, is a vibrant city.
Mistake 3: Confusing “who” and “whom”
- ❌ The person who I hired has great skills. (informal, but technically incorrect in formal writing)
- ✅ The person whom I hired has great skills.
Mistake 4: Adding a redundant pronoun
- ❌ The book that I borrowed it was fascinating.
- ✅ The book that I borrowed was fascinating.
The relative pronoun already replaces the object — you don’t need “it” again.
Mistake 5: Wrong use of “whose” vs. “who’s”
- Whose = possessive relative pronoun (the woman whose bag was stolen)
- Who’s = contraction of “who is” (a friend who’s always there for you)
Relative Pronouns vs. Relative Adverbs
Relative pronouns are often confused with relative adverbs — words like where, when, and why that also introduce relative clauses. The key difference is their function:
- Relative pronouns replace a noun in the clause.
- Relative adverbs replace an adverbial phrase (of place, time, or reason).
Examples:
- The city where I was born is beautiful. (where = in which)
- The year when I graduated was unforgettable. (when = in which)
- That’s the reason why I left. (why = for which)
Relative Pronouns in Formal vs. Informal English
Usage of relative pronouns can shift depending on the context:
- In formal writing, “whom” is preferred over “who” for objects, and “which” is used for non-defining clauses.
- In informal speech, “who” often replaces “whom,” and “that” is frequently used instead of “which.”
- Preposition placement is also more relaxed in informal English: “the person I spoke to” vs. the formal “the person to whom I spoke.”
Neither style is wrong — knowing which to use in which context is the key to communicating effectively.
Quick Summary: Relative Pronouns at a Glance
- A relative pronoun connects a relative clause to an antecedent (a noun or pronoun).
- The five main relative pronouns are: who, whom, whose, which, and that.
- Who and whom refer to people; which refers to things; that can refer to both.
- Defining clauses (no commas) give essential information; non-defining clauses (with commas) add extra detail.
- The relative pronoun can be omitted when it serves as the object of the clause.
- Avoid common errors like using “which” for people or “that” in non-defining clauses.
Conclusion
Relative pronouns — who, whom, whose, which, and that — are essential tools in English grammar. They let you link ideas smoothly, add descriptive detail, and build sentences that are both precise and elegant. Understanding when and how to use each one is a genuine upgrade to your writing and speaking ability.
The good news? Once you get a feel for how they work, using them becomes second nature. Start noticing them in the books you read and the conversations you have. The more you see them in context, the more confident you’ll become using them yourself.
Frequently Asked Questions (FAQs)
What is a relative pronoun in simple terms?
A relative pronoun is a word (like who, which, or that) that connects a descriptive clause to a noun in the main sentence. For example, in “the car that I drive,” the word “that” is a relative pronoun linking “the car” to the clause “I drive.”
What are the 5 relative pronouns in English?
The five relative pronouns in English are who, whom, whose, which, and that. Each has a specific use depending on whether the antecedent is a person or a thing, and whether the pronoun acts as a subject, object, or possessive in its clause.
Is “that” always a relative pronoun?
No. “That” can also be a demonstrative pronoun (That is my book), a demonstrative adjective (That book is mine), or a conjunction (I know that he left). It is only a relative pronoun when it introduces a clause that describes a noun, as in “the car that I drive.”
Can a relative pronoun refer to a whole clause?
Yes — which can refer to an entire preceding clause or idea, not just a single noun. For example: “She passed the exam, which surprised everyone.” Here, “which” refers to the entire situation of her passing the exam.
What is the difference between “who” and “that” when referring to people?
Both can refer to people, but there is a subtle difference. “Who” is more personal and is always grammatically correct for people. “That” can be used informally for people (“the student that passed”), but many grammarians and style guides prefer “who” when the antecedent is a person.
Can relative pronouns be omitted?
Yes, in defining relative clauses where the relative pronoun is the object of the clause. For example: “The book (that) I read was excellent.” However, you cannot omit the relative pronoun when it is the subject of the clause: “The person who called you…” — “who” cannot be dropped here.