Restrictive vs Nonrestrictive Clauses: Comma Practice

Four volunteers are waiting for workshop badges. Two have returned their forms. “The volunteers who returned their forms should collect their badges” addresses those two. Add commas around who returned their forms, and the sentence describes all four as having returned their forms. The punctuation now disagrees with the facts.

The difference between restrictive and nonrestrictive clauses starts with reference: which people or things does the writer mean? A restrictive clause helps identify them; a nonrestrictive clause adds information about people or things already identified. Once that decision is clear, the commas follow.

Identify the noun before choosing commas

A relative clause gives information about something mentioned in the main clause. Here, we're practicing relative clauses that describe a noun or noun phrase. In “The bag that has a green strap belongs to Jo,” that has a green strap describes the bag. The word or phrase it refers back to is its antecedent. These clauses often start with who, which, that, or whose, as Purdue OWL's relative-clause guide explains.

Clause type	Its job	Commas	Original example and context
Restrictive, also called defining	Helps specify which person, thing, or group you mean	No commas around the clause	Several bags are on the bench. The bag that has a green strap belongs to Jo.
Nonrestrictive, also called non-defining	Adds information about an already identified person, thing, or group	Commas set off the clause	Jo's bag has already been identified. Jo's bag, which has a green strap, is on the bench.

“Extra information” doesn't mean unimportant information. A nonrestrictive clause might report a serious problem: “Our only freezer, which stopped working overnight, needs repair.” The freezer is already identified by our only freezer. The clause tells us something about it.

A small roster makes the meaning visible

Use this imaginary workshop roster. In the sentences below, the volunteers means these four people, unless a clause narrows the group.

Volunteer	Returned the form?
Esme	Yes
Ravi	Yes
Noah	No
Lin	No

Compare these versions:

1. The volunteers who returned their forms should collect their badges.
2. The volunteers, who returned their forms, should collect their badges.

The relative clause is who returned their forms in both sentences. Its relationship to the volunteers changes.

Meaning check	Version 1: no commas	Version 2: commas
Who receives this instruction?	Esme and Ravi, identified by the clause	All four volunteers, already identified as a group
What does the clause say about forms?	The volunteers being addressed returned theirs	The whole identified group returned theirs
Does it fit the roster?	Yes	No: Noah and Lin haven't returned theirs

Version 2 is grammatically formed, but it misrepresents this roster. It would fit a different situation: all four have now returned their forms, and the writer adds that fact while instructing the whole group to collect badges.

Version 1 doesn't independently tell us what happens to Noah and Lin. They might receive a separate instruction. If you need to say that nobody else may collect a badge, make that exclusion explicit: “Only volunteers who have returned their forms may collect badges.”

A restrictive clause defines a condition or identifies a group; it doesn't prove that people outside that group exist. In this example, we know Noah and Lin exist because the roster tells us. Don't infer someone's number of friends, siblings, or possessions from one restrictive clause alone.

The deletion test needs a meaning check

Remove who returned their forms from either version and you get:

The volunteers should collect their badges.

That's a complete grammatical sentence. It still has a subject and a verb. So “Can the remaining words stand alone?” can't distinguish these two clause types.

Instead, check whether removing the clause preserves who or what the main statement refers to. With the restrictive version, the instruction loses the condition selecting Esme and Ravi. With the nonrestrictive version, the instruction still addresses the same full group; the information about forms disappears.

The MLA Style Center's removal test checks sense and identity, rather than grammatical completeness alone. Removing a nonrestrictive clause still removes a fact. It preserves the reference of the main statement, not every piece of the original sentence's meaning.

Try this sequence when editing:

1. Find the noun or noun phrase being described.
2. Use the surrounding context to identify its intended reference.
3. Decide whether the relative clause helps select that reference or adds information about it.
4. Mark the clause's full boundary, then apply the punctuation.

If the context is missing, more than one reading may be possible. Explain the readings before choosing one.

Find both ends of the clause

A nonrestrictive clause in the middle of a sentence needs an opening and a closing comma:

The west entrance, which opens at nine, is beside the ticket office.

Here, which opens at nine ends before the main verb is. Leaving out the second comma gives an incomplete pair:

Incorrect: The west entrance, which opens at nine is beside the ticket office.

The repair is a comma after nine. Don't insert it earlier, after opens: at nine belongs inside the relative clause.

At the end of a sentence, the clause has an opening comma and ends at the sentence's final punctuation:

We used the west entrance, which opens at nine.

For a restrictive clause, leave both boundaries unmarked:

The entrance that opens at nine is beside the ticket office.

This version uses opening time to identify the entrance. Adding a single comma before is would separate the whole subject, the entrance that opens at nine, from its main verb.

These commas set off a description within a sentence. Joining two independent clauses is a different task. Compare “The entrance opens at nine, it is beside the ticket office”: the comma joins two complete statements incorrectly. See comma splice vs fused sentence for repairs at that boundary.

Who, that, and which don't replace context

Who can introduce either kind of clause about people. Compare the two volunteer sentences above: the pronoun stays the same, while the commas change its role.

For things, a common American editorial convention favors that for a restrictive clause and which for a nonrestrictive one, as in the University of Wisconsin–Madison's style guide:

• Restrictive: “The folder that contains the receipts is on the shelf.”
• Nonrestrictive: “The travel folder, which contains the receipts, is on the shelf.”

That preference isn't a universal ban on restrictive which. The British Council's defining-clause lesson teaches both that and which for things. In standard British usage, “The folder which contains the receipts is on the shelf” can be restrictive, with no commas. Follow a specified classroom or publication style, but don't add commas just because you see which.

In the standard written English practiced here, don't use that to introduce a nonrestrictive relative clause. Write “The travel folder, which contains the receipts, is on the shelf.” The British Council's non-defining-clause lesson explains this rule.

Sometimes a restrictive clause has no visible relative pronoun:

• “The folder that I opened was empty.”
• “The folder I opened was empty.”

Both work. I is the subject of opened; the relative pronoun is its object and can be omitted. In “The folder that fell was empty,” that supplies the subject of fell, so it must stay in this construction. In full nonrestrictive relative clauses like the examples here, keep the relative pronoun even when it's an object: “The travel folder, which I opened, was empty.” The British Council lessons above cover these omission rules.

A name doesn't guarantee commas

Imagine two workshop volunteers are called Sam. One works at the library; the other works at a bakery. To select the first, you can write:

The Sam who works at the library will lead the tour.

The clause distinguishes the two Sams, so it is restrictive. The name alone wouldn't tell the reader which volunteer will lead.

Now suppose the reader already knows which Sam you mean:

Sam, who works at the library, will lead the tour.

The clause adds information about that identified person. Proper names often identify someone by themselves, but shared names can require more information. The British Council's non-defining-clause lesson discusses this same-name exception in its tutor replies. Use the context to decide whether the name identifies the person on its own.

Relative clause exercises with answers

For each item, write a corrected sentence or explain why it is already correct. Identify the relative clause and explain who or what the main statement describes. Each context is independent. Change a pronoun only if the requested meaning requires it.

1. Select a subset. Six parcels are on the table; two have orange stickers. The instruction applies to those two: “The parcels that have orange stickers, go upstairs.”
2. Add information. Room 8 is already identified. Mention its new windows as extra information: “Room 8 which has new windows is quieter now.”
3. Repair the boundary. Everyone knows which nurse is meant by our school nurse. “Our school nurse, who joined us in January runs the first-aid club.”
4. Keep the intended reference. The speaker means one already identified tablet and adds its purchase date: “My tablet, that I bought in March, needs charging.”
5. Use British English. Several keys are on the hook. The clause identifies the one to take: “Take the key which has a square head.”
6. Find the clause without a pronoun. We submitted several essays. Only those submitted yesterday need revision: “The essays we submitted yesterday need revision.”
7. Handle shared names. There are two people called Mira. One teaches music, and the other teaches history. Identify the music teacher: “The Mira, who teaches music, is absent.”
8. Place an end clause. The speakers have already identified the blue canoe. Add a fact about its storage: “We chose the blue canoe which is kept in the shed.”
9. Recognize missing context. No earlier sentence identifies the researchers or says how many work abroad: “The researchers who work abroad will join online.” Could a version with commas also be grammatical? Explain what each version would mean.

Check the reference and the repair

1. The parcels that have orange stickers go upstairs. The restrictive clause is that have orange stickers. It selects the two marked parcels. Remove the comma after stickers: the main subject ends there, and the main verb is go.
2. Room 8, which has new windows, is quieter now. The nonrestrictive clause is which has new windows. Room 8 is already identified; the windows don't select a room from several candidates. Add commas after 8 and windows.
3. Our school nurse, who joined us in January, runs the first-aid club. The nonrestrictive clause ends after January. Add the missing closing comma before the main verb runs. The statement still concerns the same identified nurse.
4. My tablet, which I bought in March, needs charging. The clause is which I bought in March. Keep the commas and replace that with which for this nonrestrictive meaning. Removing the commas instead would make the purchase date part of identifying the tablet, changing the requested reading.
5. Already correct. Which has a square head is restrictive: it identifies the key. Restrictive which is allowed in British English. “Take the key that has a square head” also works. Adding a comma would turn the description into supplementary information about an already identified key.
6. Already correct. We submitted yesterday is a restrictive relative clause with its object pronoun omitted. It means that we submitted yesterday. The clause identifies the essays needing revision by when we submitted them. The sentence makes no claim about essays submitted at another time. No commas belong around the clause.
7. The Mira who teaches music is absent. Remove both commas. Who teaches music selects one of the two Miras. With commas, the phrase the Mira would need to identify her without help from the clause, which this context doesn't establish.
8. We chose the blue canoe, which is kept in the shed. The clause which is kept in the shed supplies information about the already identified canoe. Add a comma after canoe. The final period closes the sentence; no second comma is needed after shed.
9. Both versions can be grammatical, with different readings. Without commas, who work abroad identifies the researchers covered by the statement about joining online. It doesn't tell us whether any other researchers exist. “The researchers, who work abroad, will join online” refers to an independently identified group and says that they all work abroad. You need context to know whether that group and that fact match the writer's intention.

Save the context on your review cards

If you miss an item, retry it before turning it into a flashcard. A card that only asks “Does who need commas?” leaves out the information required to decide. Keep the intended reference on the front and explain the punctuation on the back.

These three original cards work independently of the exercise list:

Card front	Card back
Five hikers are waiting. Two have maps. Address those two. Punctuate: The hikers who have maps should lead.	The hikers who have maps should lead. No commas: who have maps selects the two hikers addressed by this instruction.
A class has one aquarium, already identified. Repair: Our aquarium, which holds twenty litres needs cleaning.	Our aquarium, which holds twenty litres, needs cleaning. Add the closing comma after litres. The capacity is extra information; needs is the main verb.
Two neighbours are named Ali. One lives upstairs; the other lives downstairs. Identify the upstairs neighbour. Punctuate: The Ali who lives upstairs found the parcel.	The Ali who lives upstairs found the parcel. No commas: the clause distinguishes the two Alis. A shared proper name doesn't identify the neighbour by itself.

You can save these in Nibomo or another flashcard tool. For cards that require an explanation, see cloze deletion vs basic flashcards. If you're using this practice alongside exam questions, the ACT flashcard guide covers connecting review cards with broader practice.

On your next correction, write down the intended person or group first. Then mark the clause's beginning and end. That gives each comma a reason you can explain.