A relative clause is a dependent clause that can identify a person or thing or add a detail about it. Use commas when the clause adds a detail about someone or something the reader can already identify. Write a clause that identifies which people or things you mean without commas.
- The volunteers who have first-aid training will lead the hike. The sentence assigns the job to the volunteers with training.
- The volunteers, who have first-aid training, will lead the hike. The whole group will lead the hike. The commas set off the detail that they all have training.
How to spot a relative clause
In The map that shows the trail is on the desk, that shows the trail is a clause with a subject, that, and a verb, shows. It modifies the map, the noun phrase it refers back to. That noun phrase is its antecedent.
Look for a group of words that tells you which person or thing the writer means or adds information about it. Common openings include who, which, that, and where. Sometimes the opening word can be left out. In The map you borrowed is on the desk, you borrowed still identifies the map. You can also write the map that you borrowed.
When do relative clauses need commas?
A defining relative clause, also called a restrictive clause, limits what the noun refers to. In Replace the maps that show the old route, the clause tells staff which maps to replace. Write the defining clause without commas.
A nondefining relative clause, also called a nonrestrictive clause, adds information about an already identified person or thing. In This map, which shows the old route, needs replacing, this map already identifies the map. The clause adds a detail about it. Put a comma on each side when the clause appears in the middle of the sentence. At the end of the sentence, use a comma before the clause, as in We replaced this map, which showed the old route.
Try taking the clause out and asking what the shorter sentence would tell someone to do. Replace the maps still works as a sentence, but it gives a broader instruction than Replace the maps that show the old route. In This map needs replacing, the same map still needs replacing. That check works even when both shorter sentences are grammatical. Purdue OWL on defining and nondefining clauses.
Choose who, whom, whose, which, that, or where
| Word | Use | Example |
|---|---|---|
| who | A person, especially as the subject of the relative clause. | The ranger who marked the route is here. |
| whom | A person as the object of a verb or preposition, especially in formal writing. | The ranger to whom we sent the map is here. |
| whose | Possession or association with a person or thing. | The shelter whose roof needs repair is closed. |
| which | A thing or animal, in a defining or nondefining clause. | This trail, which follows the river, is open. |
| that | A person, thing, or animal, in a defining clause. | Use the path that follows the river. |
| where | A place when the clause tells you what happens there. | This is the shelter where we ate lunch. |
To choose between who and whom, look inside the relative clause. In the ranger who helped us, the ranger did the helping. In the ranger whom we helped, we did the helping. Who is common as an object in everyday English, as in the ranger who we spoke to. With a preposition directly before the pronoun, use whom for a person, as in the ranger to whom we spoke. Who vs. Whom.
In American edited prose, Chicago style favors that for defining clauses about things and which with commas for added information. Defining which is also grammatical and common in British English. When the clause adds a detail about a thing, as in this trail, which follows the river, use which with the comma. Chicago Manual of Style on which and that.
Use where when you could say there in a separate sentence. In the shelter where we ate lunch, we ate lunch there. In the shelter that we repaired, we repaired it, so use that or which. When works for times, as in the day when we left, and why works after reason, as in the reason why we left. Cambridge English Grammar Today on relative words.
When can you leave out a relative pronoun?
In a defining clause, you can usually omit the relative pronoun when it’s the object. Keep it when it’s the subject. Look for who or what does the action inside the relative clause.
- Object. The map that you borrowed is on the desk can become The map you borrowed is on the desk. You is the subject of borrowed.
- Subject. In The map that shows the trail is on the desk, keep that or use which. The relative word is the subject of shows.
- Added information. Keep which in This map, which you borrowed last week, is on the desk. Even when the pronoun is an object, a nondefining clause keeps its relative word.
You can also omit a pronoun after moving its preposition to the end of a defining clause. The trail about which we talked becomes the trail we talked about. Use the relative pronoun in place of a repeated subject or object. In the map that I borrowed, that already stands for the thing you borrowed. Cambridge English Grammar Today on defining and nondefining clauses.
Put the clause close to the words it describes
In I spoke to the assistant of the curator who organized the exhibit, the reader may wonder who organized it. If the assistant did, write I spoke to the curator’s assistant, who organized the exhibit. If the curator did, write The curator organized the exhibit. I spoke to her assistant. Two short sentences can make the connection clearer when several people or things could be the antecedent.
A relative clause with which can also refer to a whole event. In The museum extended its hours, which gave us time to visit, the extra time came from the change in hours. If the reference is hard to follow, name the event in a new sentence. The museum extended its hours. That change gave us time to visit.
Practice editing relative clauses
Add commas, choose a relative word, or revise the sentence as directed.
- The tickets that have blue stripes are valid on Friday. Only the blue-striped tickets work on Friday. Does the clause need commas?
- The west entrance which is near the station closes at six. The station detail is extra. Add commas.
- The room (where / that) we held the workshop seats 40. Choose the word that fits.
- The speaker to (who / whom) we sent the invitation accepted. Choose the form for formal writing.
- The photo that I took at sunrise won a prize. Can you omit that?
- I met the brother of the guide who marked the trail. Rewrite it to show that the brother marked the trail.
Show the answers and explanations
- The tickets that have blue stripes are valid on Friday. Use no commas. The clause identifies which tickets are valid.
- The west entrance, which is near the station, closes at six. The entrance is already identified, so set off the added detail with two commas.
- The room where we held the workshop seats 40. We held the workshop there.
- The speaker to whom we sent the invitation accepted. Whom is the object of to.
- The photo I took at sunrise won a prize. Yes. I is the subject of took, and the omitted pronoun was its object.
- I met the guide’s brother, who marked the trail. The clause now follows the guide’s brother, which makes clear who marked the trail.
