A relative pronoun is a word like who, which, or that. It begins a relative clause, a group of words that describes a noun earlier in the sentence. In “The house that Jack built is large,” the word that links the clause “Jack built” back to “the house.”
English relies on a small set of these words, and each one has its own job. This guide covers what each pronoun refers to and when a clause needs commas. It also settles the that-or-which question the way American editors do, with corrected examples throughout.
Main relative pronoun forms in English
who, whom, whose, which, and that
How Does a Relative Pronoun Work?
A relative pronoun introduces a relative clause, which is a type of dependent clause. The clause has its own subject and verb, but it can’t stand alone as a sentence. It works like an adjective, so some teachers call it an adjective clause.
The noun the clause describes is called the antecedent. In “the professor, whom I respect,” the antecedent is the word professor. The pronoun points back to that noun and connects two ideas in one sentence.
Which pronoun you choose depends on two things. The first is what the antecedent is: a person, an animal, a thing, or a whole idea. The second is whether the clause is essential to the meaning of the sentence.
Quick reference
Who, Whom, Whose, Which, and That at a Glance
| Pronoun | Refers to | Clause type | Example |
|---|---|---|---|
| who | People, and sometimes pets, as the subject | Restrictive or nonrestrictive | The nurse who answered the phone was helpful. |
| whom | People, as the object of a verb or preposition | Restrictive or nonrestrictive | The professor, whom I respect, recently received tenure. |
| whose | Possession, for people, animals, or things | Restrictive or nonrestrictive | The book whose author won a Pulitzer became a bestseller. |
| which | Animals and things, or a whole idea | Nonrestrictive in US style | The science fair, which lasted all day, ended with an awards ceremony. |
| that | People, animals, or things | Restrictive only | The house that Jack built is large. |
Based on Cambridge Dictionary, the Purdue OWL, and the UNC Writing Center, checked Oct 6, 2026. Several examples are adapted from the Purdue OWL. Full references in the Sources section.
A few other words can also do this linking job in certain sentences. The Purdue OWL notes that what, when, and where sometimes take on this role. When and where are often called relative adverbs, because they refer to a time or a place.
- When introduces a clause about a time: “The time when you should consider switching majors is now.”
- Where introduces a clause about a place: “The house where Alex grew up is only three blocks away.”
- Why introduces a clause about a reason: “That is the reason why the meeting moved to Friday.”
Relative Pronoun Examples in Sentences
Seeing these words in context is the fastest way to learn them. In each sentence below, the relative pronoun is in bold. Notice which clauses take commas and which don’t.
- The substitute who took Mrs. Lee’s place is extremely friendly.
- The dog that was sleeping earlier is now very energetic.
- The family spent a week at Disney World, which is celebrating its anniversary.
- Sarah, whose brother lives in New York, decided to spend a day in the city.
- The artist whom you praised was quite popular in the 19th century.
- I have a friend whose mom is a doctor.
Restrictive vs. Nonrestrictive Clauses: When to Use Commas
Every relative clause is either restrictive or nonrestrictive. They are also known as defining and non-defining clauses. The difference decides whether you need commas, and in American English it also guides your choice of pronoun.
Restrictive (Defining) Clauses
A restrictive clause gives information you need to identify the noun. Take it out, and the sentence loses its meaning or says something different. Restrictive clauses never take commas, and they can begin with that, who, whom, or whose.
- This is the student who won the academic scholarship.
- People who like history enjoy visiting the Smithsonian museums.
- The band received a list of performance dates that have sold out.
- Students whose grades are low can drop one test score.
Nonrestrictive (Nondefining) Clauses
A nonrestrictive clause adds extra detail about a noun that is already clear. You could remove it and the main point would stay the same. Set it off with commas on both sides, or with one comma when it ends the sentence.
- The flower, which sits on the windowsill, is starting to bloom again.
- Mr. Adams, who spent all summer in California, is the new English teacher.
- My brother, whose car I’m driving, visited a few colleges last week.
- My mother, who is an excellent cook, is thinking of opening a restaurant.
That or Which? The American Rule
In American English, use that for restrictive clauses and which with commas for nonrestrictive ones. The Chicago Manual of Style gives a pizza example. “Pizza that’s less than an inch deep just isn’t Chicago-style” needs its clause, so it takes that. In “Pizza, which is a favorite among Chicagoans, can be either bad for you or good,” the clause is extra, so it takes which.
A commaless-that clause narrows (restricts) the meaning; a comma-plus-which doesn’t narrow (it’s called nonrestrictive).
Bryan A. Garner, LawProse Lesson #126 (2013)
British writers often use which without commas in restrictive clauses. Chicago calls this “more or less okay.” Most US editors still change it to that. One exception applies to everyone: after a preposition, use which, as in “all the cases in which the judge recused herself.”
That has one more limit. It can’t introduce a nonrestrictive clause, so “I’m planning to grow roses, that I find quite beautiful” is wrong. Swap in which and the sentence works.
Who or Whom: How to Choose
Use who when the pronoun acts as the subject of its clause, and whom when it acts as the object. A quick test helps: if he, she, or they would fit, choose who. If him, her, or them would fit, choose whom.
“The nurse who helped us” works because she helped us. “The visitor for whom you were waiting has arrived” works because you were waiting for him. Whom is formal, and the Purdue OWL notes that Americans rarely use it in speech. Still, keep it directly after a preposition, where who would be incorrect.
Both who and that can refer to people in restrictive clauses, so “the person that called” is acceptable. That said, the Purdue OWL notes that who is more common in formal writing. Which refers to animals and things, not people.
When Can You Leave Out the Relative Pronoun?
You can often drop the relative pronoun when it is the object of a restrictive clause. You can shorten “the book that I wanted” to “the book I wanted” without changing the meaning. Both versions are correct, and the Purdue OWL classes the shorter one as informal English.
Two situations keep the pronoun in place. In “the dog that bit me,” the pronoun is the subject of the clause, so it must stay. A nonrestrictive clause also keeps its pronoun, as with which in “the house, which my grandfather built, needs renovating.”
Read the sentence without the clause. If the meaning stays the same, the clause is nonrestrictive: use which and set it off with commas. If the meaning changes, the clause is restrictive: use that and skip the commas.
Common Relative Pronoun Mistakes and How to Fix Them
Most errors with these words come down to commas, agreement, or the wrong pronoun for the antecedent. Each example below shows the mistake first, then the fix.
- Using that after a comma. Incorrect: “I’m planning to grow roses, that I find quite beautiful.” Correct: “I’m planning to grow roses, which I find quite beautiful.”
- Forgetting the second comma. Incorrect: “My mother, who is an excellent cook is opening a restaurant.” Correct: “My mother, who is an excellent cook, is opening a restaurant.”
- Using who for things. Incorrect: “There are some art books who you can get ideas from.” Correct: “There are some art books that you can get ideas from.”
- Breaking subject-verb agreement. Incorrect: “We met the women who owns this hotel.” Correct: “We met the women who own this hotel.”
- Putting who after a preposition. Incorrect: “She’s the one on who I rely.” Correct: “She’s the one on whom I rely.”
Agreement trips up even confident writers. The verb in the clause must match the antecedent, not the pronoun itself. “People who win the lottery” takes a plural verb, while “a person who wins the lottery” takes a singular one.
Sources
- "Relative Pronouns," Cambridge Dictionary, English Grammar Today. Available at: https://dictionary.cambridge.org/grammar/british-grammar/relative-pronouns. Accessed 6 Oct. 2026.
- "Relative Pronoun," Cambridge Learner’s Dictionary. Available at: https://dictionary.cambridge.org/dictionary/learner-english/relative-pronoun. Accessed 6 Oct. 2026.
- "Introduction and General Usage in Defining Clauses," Purdue OWL, Purdue University. Available at: https://owl.purdue.edu/owl/general_writing/grammar/relative_pronouns/index.html. Accessed 6 Oct. 2026.
- "Relative Pronouns in Non-defining Clauses," Purdue OWL, Purdue University. Available at: https://owl.purdue.edu/owl/general_writing/grammar/relative_pronouns/relative_pronouns_in_non_defining_clauses.html. Accessed 6 Oct. 2026.
- "Relative Clauses," The Writing Center, University of North Carolina at Chapel Hill. Available at: https://writingcenter.unc.edu/tips-and-tools/relative-clauses/. Accessed 6 Oct. 2026.
- "Which vs. That," Chicago Style Q&A, The Chicago Manual of Style Online, University of Chicago Press. Available at: https://www.chicagomanualofstyle.org/qanda/data/faq/topics/Whichvs.That.html. Accessed 6 Oct. 2026.
- "LawProse Lesson #126: “That” vs. “which”," Bryan A. Garner, LawProse, 2013. Available at: https://lawprose.org/lawprose-lesson-126-that-vs-which/. Accessed 6 Oct. 2026.
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