Relative Clauses
Learn how a relative clause describes a noun, which relative pronoun to use, and why commas around the clause can change the meaning of the sentence.
Describing a noun
A relative clause adds detail to a noun already named.
A relative clause describes a noun, using a relative pronoun to attach the description directly to the noun it modifies.
In the man who called, the clause who called describes the noun man, using the relative pronoun who to identify which man is being talked about.
Whether a relative clause is set off with commas depends on whether the detail it adds is essential to identifying the noun, or simply extra information about it.
Before you begin
Relative clauses are one of five clause types.
This lesson focuses on relative clauses specifically. Clauses as a whole include four other types, each covered in its own lesson.
If you would like an overview of how clauses work in general, begin with the Clauses page.
The central idea
A relative clause narrows down which noun is meant.
Compare a plain noun with the same noun described by a relative clause.
01
Plain noun
the man
02
Noun with a relative clause
the man who called
The useful question is: which noun is being described, and by what?
Who called attaches directly to man, narrowing the plain noun down to one specific person.
The relative pronouns
Each relative pronoun connects to a different kind of noun or role.
who → a person, as the subject: the man who called
whom → a person, as the object: the man whom she called
whose → showing possession: the man whose car broke down
which → a thing: the car which broke down
that → a person or thing, in a restrictive clause: the man that called
Whom is more formal
Whom is used for a person receiving the action, but who is commonly used in its place in everyday speech and writing.
Restrictive and non-restrictive clauses
Commas around the clause change what is being said.
Compare a clause that identifies the noun with one that simply adds extra detail.
Restrictive: essential to identifying the noun
The man who called left a message.
No commas are used. The clause identifies which man is meant; removing it would leave the noun unclear.
Non-restrictive: extra, non-essential detail
My brother, who lives in Chicago, is visiting.
Commas are used. The noun, my brother, is already identified; the clause simply adds extra information that could be removed without losing the core meaning.
Omitting the relative pronoun
A relative pronoun can sometimes be left out.
the book (that) I read
When the relative pronoun is the object of the clause, rather than the subject, it can often be omitted in a restrictive clause without changing the meaning.
A useful decision guide
Ask what the clause describes, and whether it is essential.
01
Is the noun a person or a thing?
Choose who/whom/whose for people, which for things.
02
Is the relative pronoun the subject or the object of the clause?
An object pronoun can sometimes be omitted in a restrictive clause.
03
Is the clause needed to identify the noun?
If so, it is restrictive, and no commas are used.
04
Could the clause be removed without losing the core meaning?
If so, it is non-restrictive, and commas are used.
Common mistakes
Commas around a relative clause change what the sentence says.
A non-restrictive clause needs commas.
Not: My brother who lives in Chicago is visiting. (if there is only one brother)
Correct: My brother, who lives in Chicago, is visiting.
Without the commas, the sentence implies there is more than one brother, and the clause is needed to identify which one.
A restrictive clause does not take commas.
Not: The man, who called, left a message.
Correct: The man who called left a message.
The clause is needed to identify which man is meant, so no commas are used.
Which describes a thing, not a person.
Not: The man which called left a message.
Correct: The man who called left a message.
Check your understanding
Which relative pronoun correctly completes each sentence?
Choose the correct answer for each sentence.
The woman __________ car broke down called for help.
✅ Exactly! Whose shows that the car belongs to the woman.
❎ Not quite. Check whether this word is showing possession.
Whose car is it?
The car __________ broke down is now being repaired.
✅ Exactly! Which is used for a thing, not a person.
❎ Not quite. Is a car a person or a thing?
What noun is this clause describing?
The students who studied hard passed the exam.
✅ Exactly! The clause identifies which students are meant, and no commas are used.
❎ Not quite. Look at whether commas are used, and whether the clause is essential.
Is the clause set off with commas?
Choose the best explanation
Select the sentence that explains the relative clause correctly.
Why does “My brother who lives in Chicago is visiting.” need commas, if there is only one brother?
✅ Exactly! Commas mark the clause as extra detail rather than essential identification.
❎ Not quite. Think about what the commas signal about the clause’s role.
Why is “The man, who called, left a message.” not correctly punctuated?
✅ Exactly! This clause is restrictive, so no commas are used.
❎ Not quite. Ask whether the clause is essential to identifying the man.
Try it another way
Add commas where they are needed.
Type the sentence again, adding commas around the relative clause if it is non-restrictive.
Our teacher who studied in Paris speaks fluent French. (there is only one teacher)
✅ Exactly! With only one teacher, the clause is extra detail and takes commas.
❎ Not quite. Since there is only one teacher, this clause is not essential to identifying who is meant.
The book that won the award is on the shelf. (one of several books)
✅ Exactly! This clause identifies which book among several, so no commas are needed.
❎ Not quite. This clause is essential to identifying which book is meant.
Quick review
A relative pronoun connects a description to the noun it modifies.
A relative clause describes a noun, using a relative pronoun such as who, whom, whose, which or that.
A restrictive clause is essential to identifying the noun and takes no commas; a non-restrictive clause adds extra detail and is set off with commas.
An object relative pronoun can sometimes be omitted in a restrictive clause.
Who and whom refer to people; which refers to things; that can refer to either, in a restrictive clause.
Remember
Ask whether the clause is essential, or just extra detail.
If removing the clause would leave the noun unclear, keep it without commas. If the noun is already clear on its own, set the clause off with commas.