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I’ll never forget my student Tariq asking, “Teacher, why do native speakers keep adding extra parts to their sentences? Why not just say ‘The man is my uncle’ instead of ‘The man who was wearing a red hat is my uncle’?” That’s when I realized adjective clauses are the secret behind complex, interesting English writing. They let you build layer upon layer of detail without breaking up your sentence into choppy fragments.
Adjective clauses (also called relative clauses) are subordinate clauses that modify nouns and pronouns by providing extra information. They’re introduced by relative pronouns (who, which, that, whose) or relative adverbs (where, when, why), and they’re one of the most powerful tools for upgrading your writing from flat to fluent.
Key Takeaways
- Function as adjectives — they describe and modify nouns, answering “which one?” or “what kind?”
- Introduced by relative pronouns or adverbs — who, whom, whose, which, that (pronouns) or where, when, why (adverbs).
- Two types: defining (essential to meaning, no commas) and non-defining (extra info, with commas).
- Word order matters — the clause usually follows immediately after the noun it modifies.
- Master these to write complex, adult-level English without awkwardness.
What Are Adjective Clauses?
An adjective clause is a group of words containing a subject and a verb that modifies (describes) a noun or pronoun. Unlike a single adjective (e.g., “red”), an adjective clause is an entire clause — it has its own verb and can add rich, specific information.
Simple adjective: The red car is fast.
Adjective clause: The car that I bought last year is fast.
In my classroom, I tell students: an adjective clause is a sentence within a sentence, and it’s attached to a noun to tell you more about that noun.
More examples:
Example 1: The woman who was speaking at the conference was an expert in her field. (Clause answers “which woman?”)
Example 2: I visited the city where I grew up. (Clause answers “which city?” and why it’s special.)
Example 3: The book that I’m reading is a bestseller. (Clause answers “which book?”)
Types of Adjective Clauses: Defining vs. Non-Defining
There are two main types, and the difference is crucial for comma placement and meaning.
Defining (Restrictive) Clauses
A defining adjective clause provides essential information — information you need to identify which specific noun you’re talking about. No commas.
Example: The person who is wearing a red hat is my uncle.
Why? Because without the clause, “The person is my uncle” could refer to anyone. The clause is essential to understanding which specific person.
Another example: I love movies that have a twist ending.
Why? Without the clause, “I love movies” is vague. The clause tells you which kind of movies.
Non-Defining (Non-Restrictive) Clauses
A non-defining adjective clause provides extra information about a noun that’s already clear or fully identified. Use commas.
Example: My uncle, who was wearing a red hat, is visiting next week.
Why? Because I’ve already told you who “my uncle” is. The clause is extra detail, so it’s set off by commas.
Another example: The Harry Potter series, which J.K. Rowling wrote, changed children’s literature.
Why? The reader already knows which series you mean. The clause just adds extra context.
Comma rule: If the noun is already specific or fully identified, use commas around the clause. If you need the clause to identify which noun, don’t use commas.
Relative Pronouns: Who, Whom, Whose, That, Which
| Relative Pronoun | Use When… | Function | Example |
|---|---|---|---|
| Who | Referring to a person (subject of clause) | Subject | The manager who hired me is helpful. |
| Whom | Referring to a person (object of clause) | Object | The manager whom I met is helpful. (I met the manager) |
| Whose | Showing possession | Possessive | The student whose essay won is celebrating. |
| That | Defining clauses (people, things, animals) | Subject or object | The book that I read was excellent. |
| Which | Non-defining clauses (things, animals) | Subject or object | The book, which won an award, is excellent. |
Relative Adverbs: Where, When, Why
Instead of pronouns, adjective clauses can be introduced by relative adverbs that describe place, time, or reason.
Where (place): The city where I spent my childhood is beautiful.
When (time): I’ll never forget the day when we first met.
Why (reason): The reason why I left was my family’s move.
Forming Adjective Clauses: The Pattern
Most adjective clauses follow a predictable pattern:
[Noun] + [Relative pronoun/adverb] + [Subject (optional)] + [Verb] + [Rest of clause]
Example breakdown:
The car | that | (no subject — that is subject) | was stolen | last night.
Noun | pronoun | | verb | object
Another example:
The student | whom | I | taught | five years ago.
Noun | pronoun | subject | verb | (object is “whom”)
Real examples:
Example 1: The movie that I watched yesterday was amazing. (Defining; no commas)
Example 2: My father, who is 65 this year, is retiring. (Non-defining; commas)
Example 3: This is the reason why I came late. (Why clause)
Common Mistakes Learners Make
✗ Incorrect: The woman who I met is a doctor.
✓ Correct: The woman whom I met is a doctor.
Why: The woman is the object of the verb “met,” so use “whom” (not “who”). But note: many native speakers now use “who” here too, especially in casual speech.
✗ Incorrect: The book which is on the table is mine.
✓ Correct: The book that is on the table is mine.
Why: This is a defining clause (essential info to identify which book), so “that” is more standard in American English than “which.” British English is more flexible.
✗ Incorrect: I visited the city, where I grew up.
✓ Correct: I visited the city where I grew up.
Why: This is a defining clause (necessary to identify the city), so no comma. Only use commas for non-defining clauses.
✗ Incorrect: The book, that I am reading, is really good.
✓ Correct: The book that I am reading is really good.
Why: Defining clauses use “that” without commas. If you use commas, switch to “which.”
Two students discussing an assignment
Maria: I don’t understand this sentence. “The student who forgot to submit the assignment will lose points.”
Jake: It’s an adjective clause. The main sentence is “The student will lose points.” The part “who forgot to submit the assignment” is extra info.
Maria: So “who” is like an adjective here?
Jake: Exactly. It describes which student you’re talking about. That’s why it’s called an adjective clause.
Maria: Got it. And if it was “The student, who forgot to submit the assignment, will lose points”?
Jake: Then you’re talking about a specific student you already know. The clause is just adding extra context.
Quick Quiz
Identify the adjective clause and choose the correct relative pronoun:
- The teacher _______ gave us homework is strict. (who / that)
- The city _______ I was born is very crowded. (where / when)
- The reason _______ I didn’t attend the party was illness. (why / when)
- My friend, _______ just moved to Toronto, is excited about the change. (who / that)
- The book _______ I borrowed from you is fascinating. (which / that)
Answers: 1. who (or that) — defines which teacher · 2. where — refers to place · 3. why — refers to reason · 4. who — non-defining (commas), so “who” is more standard · 5. that — defining clause, “that” is standard in American English
Reducing Adjective Clauses
Advanced writers sometimes remove part of the clause to create a more concise style. This is called a “reduced adjective clause.”
Full clause: The person who is standing by the window is my brother.
Reduced: The person standing by the window is my brother.
Full clause: The award, which was given last night, was well-deserved.
Reduced: The award, given last night , was well-deserved.
Reduced clauses are common in advanced writing and are good to recognize, but don’t worry about forming them until you’re confident with full adjective clauses.
Related Grammar Topics
- Possessive Adjectives (My, Your, His, Her)
- Interrogative Adjectives (What, Which, Whose)
- Noun Clauses: Dependent Clauses as Subjects and Objects
- Relative Pronouns: Who, Whom, Whose, That, Which
- ↑ Back to pillar: English Adjectives (Pillar)
Frequently Asked Questions
What’s the difference between an adjective clause and an adverb clause?
Adjective clauses modify nouns and answer “which one?” or “what kind?” (Example: “The book that I read” — modifies “book”). Adverb clauses modify verbs, adjectives, or entire sentences and answer “when?”, “where?”, “why?” as separate clauses (Example: “I went home because I was tired” — modifies “went”).
Do I need a comma before adjective clauses?
Only if the clause is non-defining (non-essential). “The car that I drove is broken” (no comma — defining). But “My car, which is blue, is broken” (commas — non-defining, already identified).
Can I use “that” in place of “who” or “which”?
In defining clauses, yes — “that” works for people, animals, and things. “The person that helped me” or “The book that I read.” But in non-defining clauses with commas, use “who” for people and “which” for things. Never “that” with commas.
What’s the difference between “who” and “whom”?
“Who” is the subject of the clause; “whom” is the object. “The teacher who taught me” (subject) vs. “The teacher whom I thanked” (object). In casual speech, many speakers just use “who” for both.
Can adjective clauses come at the beginning of a sentence?
Rarely, and usually only in formal or poetic writing. “The book that changed my life was small” works naturally. But “That changed my life, the book was small” is awkward. Adjective clauses normally follow the noun they modify.
How do I know if my adjective clause is correct?
Check these: (1) Is it modifying a noun? (2) Does it have a subject and verb? (3) Is the relative pronoun or adverb correct for its function? (4) Are commas correct (commas = non-defining; no commas = defining)? If yes to all, you’re good.
Related
- ↑ Master Pillar: English Grammar
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