A defining relative clause tells the listener exactly which person, thing or place you mean. Without it, the sentence would be unclear. It comes right after the noun and never has commas around it.
The pattern
The woman who lives next door is a nurse.
This is the coffee shop where we met.
01People: who or that
For people, use who. That is also correct and very common in conversation, but who is the safer choice in writing.
- I have a friend who works at Google.
- The guy that fixed my sink was really fast.
02Things: that is the American choice
For things and animals, American English strongly prefers that in defining clauses. Which is used mainly in non-defining clauses, the kind with commas that add extra information. Most US editors and style guides follow this rule, so "the laptop that I bought" looks right to American readers.
British English uses which here much more freely, so you'll see both in books and online.
- The laptop that I bought last week already has a problem.
- Is this the train that goes to Union Station?
- My car, which is ten years old, still runs great. (extra information, commas)
03Places and possession: where and whose
Use where for places when a full clause follows (subject + verb). Use whose to show that something belongs to the person or thing before it.
- That's the hospital where I was born.
- I work with a guy whose wife is a pilot.
04When you can leave the word out
If the relative word is the object of the clause (another subject comes right after it), you can drop it. Americans do this all the time in speech. If it is the subject (a verb comes right after it), you must keep it.
| Relative word is... | Example | Can you drop it? |
|---|---|---|
| the object | The movie (that) we watched was boring. | Yes |
| the object | The people (who) I met at the party were nice. | Yes |
| the subject | The man who called you is my boss. | No |
05Common mistakes
The man which fixed my sink was great.
The man who fixed my sink was great.
Use who or that for people, not which.
This is the restaurant where we ate there last week.
This is the restaurant where we ate last week.
Where already means there, so don't repeat it.
I have a friend lives in Miami.
I have a friend who lives in Miami.
When the relative word is the subject, you can't leave it out.
The phone, that I bought online, stopped working.
The phone that I bought online stopped working.
Defining clauses have no commas.