Restrictive And Nonrestrictive Relative Clauses | Rules

English sentences often carry extra information about a person, thing, place, or time. A common way to add that information is with a relative clause that starts with words such as who, which, or that. Some of these clauses are needed to identify the noun, and some only add side notes. That difference sits at the center of restrictive and nonrestrictive relative clauses.

Once you learn how these two clause types work, commas make more sense, your writing feels clearer, and exam questions on relative clauses stop feeling like a puzzle. This guide walks through the meanings, punctuation, and pronoun choices step by step, with plenty of examples you can adapt in your own writing for learners.

Teachers, exam writers, and style guides often use the names defining and non-defining instead of restrictive and nonrestrictive. The ideas match. A defining or restrictive clause narrows down which person or thing you mean. A non-defining or nonrestrictive clause gives extra detail about someone or something the reader can already identify.

What Are Restrictive And Nonrestrictive Relative Clauses?

A relative clause adds information about a noun and usually begins with a relative pronoun such as who, whom, which, that, whose, where, or when. It can be restrictive or nonrestrictive. The choice tells the reader how closely the information links to the main noun.

In short, a restrictive relative clause is needed to identify the noun. It limits the meaning. A nonrestrictive relative clause adds extra information. The main meaning of the sentence still works even if that clause disappears.

The table below sums up the core contrasts before we study each type in detail.

Feature	Restrictive Clause	Nonrestrictive Clause
Main purpose	Identifies which person or thing you mean	Adds extra information about a known person or thing
Effect on meaning	Clause is needed; removing it changes the basic idea	Clause is optional; removing it keeps the core idea
Punctuation	No commas around the clause	Comma or commas set the clause off from the rest
Common pronouns	who, that, which, whose, where, when	who, which, whose, where, when (not that)
Spoken voice	Usually no pause before or after the clause	Clear pause before and after the clause
Example	The students who studied passed the test.	The students, who studied hard, passed the test.
Also called	Defining relative clause	Non-defining relative clause

Restrictive Relative Clauses In Simple Terms

A restrictive relative clause tells the reader exactly which person or thing you mean. Without that clause, your sentence may sound half finished or too vague. The clause restricts the noun to a smaller group.

Check these pairs of sentences:

• The students who studied passed the test. (Only the students who studied passed.)
• The people who live on this street recycle their rubbish. (Not all people, only those on this street.)

In both examples, the relative clause singles out a smaller group. If you remove the clause, the meaning changes in a serious way. For this reason, you do not place commas around restrictive clauses.

Nonrestrictive Relative Clauses In Simple Terms

A nonrestrictive relative clause gives extra detail that readers do not need in order to know who or what you mean. This clause behaves like an aside. In writing, commas show that the clause can be lifted out without breaking the sentence.

Study these pairs:

• My sister, who lives in Canada, is visiting next month. (You already know which sister. The clause just adds where she lives.)
• Paris, which is famous for its landmarks, attracts many tourists. (We all know Paris; the clause adds more detail.)

If you delete the clause between commas, the main message still works: My sister is visiting next month. Paris attracts many tourists. In nonrestrictive clauses the pronoun that does not fit, and standard style guides ask for who or which instead.

Restrictive Vs Nonrestrictive Clauses In Sentences

Writers often feel unsure about commas with relative clauses, especially when a sentence looks long. A simple test can help. Ask yourself two quick questions: “Do I need this clause to know which person or thing the sentence talks about?” and “Can the clause drop out while the basic message stays clear?”

If you need the clause to point to the right person or thing, then you have a restrictive clause and you skip commas. If the clause only adds background detail, you have a nonrestrictive clause and you set it off with commas.

Many grammar references, such as the Cambridge English Grammar Today entry on relative clauses, show this split between defining and non-defining clauses. The rule is not just a matter of style; it protects the meaning of your sentences.

Meaning Changes Caused By Commas

A short change in punctuation can reverse the sense of a sentence. Compare these lines:

• Children who eat vegetables stay healthy.
• Children, who eat vegetables, stay healthy.

In the first sentence, the clause who eat vegetables narrows the group. It suggests that only the children who eat vegetables stay healthy. In the second sentence, commas show a nonrestrictive clause. Now the idea sounds closer to “children, and they eat vegetables, stay healthy”. The sentence hints that all children eat vegetables, which may not be what you intend.

When you choose between restrictive and nonrestrictive relative clauses, you are in fact choosing between two meanings. The commas send a signal about how wide or narrow the noun group is.

Pronoun Choice: Who, Which, And That

The relative pronoun you pick can also point to clause type. Many teachers tell students that that introduces restrictive clauses and which introduces nonrestrictive clauses. Real usage is a bit more flexible, but some safe rules help.

• Use who or whom for people.
• Use which for things and animals.
• Use that only in restrictive clauses, never in nonrestrictive clauses.

The British Council LearnEnglish guide to non-defining relative clauses stresses this last point: in clauses with commas, that drops out and who or which take its place.

Using Restrictive And Nonrestrictive Clauses In Real Writing

Now that the basic contrast is clear, you can review typical sentence patterns. Seeing full examples helps you notice clause type quickly when you read and gives you patterns you can copy when you write.

Typical Patterns For Restrictive Clauses

Most restrictive clauses follow a noun directly, use no commas, and contain a relative pronoun as subject or object. Here are some common shapes:

• Subject relative clause: The man who called yesterday left a message.
• Object relative clause: The book that you lent me was helpful.
• Possessive relative clause: The singer whose songs you like is on stage tonight.
• Place and time clauses: The town where I grew up has changed a lot. The year when we met feels distant now.

In each line, the clause limits the noun. Which man? The one who called yesterday. Which book? The one that you lent me. If the clause disappears, the sentence still has grammar, but the reader loses a main part of the message.

Typical Patterns For Nonrestrictive Clauses

Nonrestrictive clauses also follow the noun, but the commas let them float as extra detail. They often feel like a side comment that the writer has chosen to share.

• Subject relative clause: My neighbour, who teaches maths, helped me with the problem.
• Possessive relative clause: Our car, whose engine is new, rarely breaks down.
• Place and time clauses: London, where my grandparents met, has changed a lot. That summer, when we first travelled abroad, stays in my memory.

If you read these sentences aloud, you will hear a short pause before and after the nonrestrictive clause. That pause matches the commas on the page and signals that the sentence would still stand without the extra information.

Punctuation Rules For Relative Clauses

Once you understand meaning, punctuation becomes easier to handle. Still, it helps to have a short set of rules to check against your own writing. The next list gathers the most practical points for restrictive and nonrestrictive clauses.

Comma Rules You Can Rely On

• Do not place a comma before a restrictive relative clause.
• Place commas before and after a nonrestrictive clause that sits in the middle of a sentence.
• Use one comma before a nonrestrictive clause that comes at the end of a sentence.
• Keep the comma close to the noun the clause refers to; avoid long gaps.
• Do not combine that with commas around the clause.

Writers sometimes mix these rules when they edit a sentence and keep an old comma by mistake. A quick reread aloud often reveals where the real pause falls and which type of clause you have created.

Relative Pronouns And Omitted Pronouns

In many restrictive clauses, the relative pronoun acts as an object and can drop out: “The book (that) you lent me was helpful.” This shortcut does not work in nonrestrictive clauses, where the pronoun stays in place between commas.

Here is a short guide you can use while you write.

Pronoun	Typical Use	Omission Allowed?
who	People, subject or object	Only in restrictive clauses, when object
whom	Formal object form for people	Only in restrictive clauses; often replaced by who
which	Things and animals	Only in restrictive clauses, when object
that	People, things, and animals in restrictive clauses	Often in speech, never with commas
whose	Possession for people, things, or animals	No
Where / when	Places and times	No

Common Mistakes With Relative Clauses

Even advanced learners slip when they mix meaning, pronoun choice, and punctuation. The good news is that most errors fall into a small group of patterns. Once you know them, they are easier to spot and fix.

Using That In A Nonrestrictive Clause

Writers often carry over that from speech and put it into clauses with commas:

Wrong: My bike, that I bought last year, is still in good shape.

Better: My bike, which I bought last year, is still in good shape.

In nonrestrictive clauses, switch from that to which or who, and keep the commas.

Missing Or Extra Commas

Another frequent issue lies in commas that do not match clause type:

Wrong: The students, who studied hard, passed the test. (if you mean only some students)

Better: The students who studied hard passed the test.

Ask yourself whether the clause narrows the group or only comments on it. Then adjust the commas to match.

Unclear Or Repeated Subjects

Learners sometimes repeat the subject before and inside the clause:

Wrong: She is the manager who she handles customer complaints.

Better: She is the manager who handles customer complaints.

The relative pronoun already acts as subject, so extra subjects confuse many readers.