Adjective Clauses: Relative Clauses That Describe a Noun
An adjective clause is a group of words with its own subject and verb that together modifies a noun. In the engineer who fixed the boiler left early, the underlined clause describes the engineer – and it contains a subject (who) and a verb (fixed) of its own.
That subject-and-verb is the whole difference between a clause and a phrase. The engineer eager to leave is an adjective phrase; add a subject and a finite verb and it becomes a clause.
The relative pronouns
| Pronoun | Used for | Example |
|---|---|---|
| who | people, as subject | the woman who called |
| whom | people, as object | the woman whom we called |
| whose | possession, people or things | the car whose alarm failed |
| which | things | the report which arrived late |
| that | people or things, defining only | the report that arrived late |
Whom is dying in speech and survives in formal writing. If you are unsure, rebuild the clause as a plain sentence and substitute he or him: we called him, so whom. He called, so who.
The commas change the meaning
This is the part worth getting right, because the punctuation is not decoration – it decides what the sentence claims.
- Defining (no commas): The staff who trained in March passed. Only some of the staff trained in March, and only those passed.
- Non-defining (commas): The staff, who trained in March, passed. All the staff trained in March, and all passed.
Two commas turn a filter into an aside. In a contract or a report that difference is worth money, which is why editors treat it as more than a style point.
Two rules follow from it. That cannot introduce a non-defining clause – write which after a comma. And a non-defining clause cannot drop its pronoun, while a defining one often can.
When you can drop the pronoun
If the relative pronoun is the object of its clause, English lets you delete it: the book that I ordered and the book I ordered are both correct. If it is the subject, it has to stay: the book that arrived cannot become the book arrived, which says something else entirely.
When to cut the clause instead
Adjective clauses are often longer than the job requires. Removing the pronoun and its verb usually leaves a tighter sentence that means exactly the same thing.
- the candidates who were eager to begin → the candidates eager to begin
- the report which was written in June → the report written in June
Do this once per sentence and the prose tightens noticeably. What is left behind is an adjective phrase, doing the same work in fewer words.
Practice
Comma, no comma, or which pronoun? Answers below.
- The tenants ___ paid on time were not affected. (defining)
- My brother ___ lives in Leeds is visiting. (I have one brother)
- The laptop ___ screen cracked is still under warranty.
- The report ___ I submitted on Friday has been approved.
- She thanked the driver ___ had waited for her.
Answers
| # | Answer | Why |
|---|---|---|
| 1 | who / that, no commas | it filters which tenants are meant |
| 2 | , who lives in Leeds, | one brother, so the clause is an aside |
| 3 | whose | possession, and it works for things |
| 4 | that / which, or nothing | the pronoun is the object, so it can be dropped |
| 5 | who | subject of its own clause, so it cannot be dropped |
Checked against Merriam-Webster, the Chicago Manual of Style and the AP Stylebook. Spotted an error? Tell us — see our editorial policy.
