Adjective Clauses (Relative Clauses): English Grammar Guide

Adjective clauses, also known as relative clauses, are an essential part of English grammar that help add detail, clarify meaning, and connect ideas smoothly. They act like adjectives by describing or modifying nouns or pronouns. Understanding adjective clauses allows you to write and speak more precisely and naturally.

What Is an Adjective Clause?

An adjective clause is a group of words that has a subject and a verb and functions as an adjective. It describes a noun or pronoun in the main clause.

For example:

• The book that I borrowed from the library is interesting.

• The person who called you is my teacher.

In both examples, the adjective clause provides extra information about the noun (“book” or “person”).

An adjective clause usually begins with a relative pronoun (such as who, whom, whose, which, that) or a relative adverb (such as where, when, why).

Structure of an Adjective Clause

The basic structure looks like this:

[Noun] + [Relative pronoun/adverb] + [Subject + Verb]

Example:

• The city where I was born is beautiful.

Here:

• The city = noun being described

• where I was born = adjective clause

Common Relative Pronouns

1. Who – refers to people (as the subject of the clause)

   • The woman who lives next door is very friendly.

2. Whom – refers to people (as the object of the clause, more formal)

   • The person whom you met yesterday is my cousin.

3. Whose – shows possession

   • The man whose car was stolen reported it to the police.

4. Which – refers to things or animals

   • The laptop which I bought last week is already broken.

5. That – can refer to people, animals, or things (used in restrictive clauses)

   • The movie that we watched last night was fantastic.

Relative Adverbs

1. Where – refers to a place

   • The café where we met has closed down.

2. When – refers to a time

   • I remember the day when we first met.

3. Why – refers to a reason

   • I don’t know the reason why he left early.

Restrictive vs. Non-Restrictive Clauses

1. Restrictive (Defining) Clauses

These are essential to the meaning of the sentence. Without them, the sentence’s meaning changes. They are not separated by commas.

Example:

• The student who studies hard will pass the exam.
  (This identifies which specific student.)

2. Non-Restrictive (Non-Defining) Clauses

These give extra information that is not essential to the meaning. They are set off by commas.

Example:

• My brother, who lives in Manila, is a doctor.
  (The clause adds more detail but doesn’t identify which brother.)

Omitting the Relative Pronoun

In some cases, especially in informal English, the relative pronoun can be omitted when it acts as the object of the clause.

Example:

• The book (that) I read was amazing.

• The person (whom) we met was kind.

Here, “that” or “whom” can be dropped without changing the meaning. However, you cannot omit the pronoun if it’s the subject of the clause:

• ✅ The man who helped me was generous.

• ❌ The man helped me was generous. (incorrect)

Using “That” or “Which”

In restrictive clauses (where the information is essential), use that.

• The car that I bought is new.

In non-restrictive clauses (extra information), use which.

• My car, which I bought last year, is still in good condition.

This distinction is especially important in formal writing.

Examples and Explanation

Example 1

• The teacher who taught me English moved abroad.
  → “Who taught me English” describes the noun “teacher.”

Example 2

• The restaurant that serves Italian food is popular.
  → The adjective clause identifies which restaurant.

Example 3

• My laptop, which I bought in 2020, still works well.
  → This adds extra, non-essential information.

Example 4

• The city where I studied has changed a lot.
  → “Where I studied” describes “city.”

Example 5

• I still remember the time when we traveled together.
  → The clause modifies “time.”

Punctuation Rules

• Do not use commas with restrictive (essential) clauses.

• Use commas to separate non-restrictive (non-essential) clauses.

• Avoid mixing them up, as it can change the meaning:

  • The students who failed the test must retake it. (Only those students)

  • The students, who failed the test, must retake it. (All students failed)

Common Mistakes

1. Using the wrong relative pronoun

   • ❌ The man which helped me.

   • ✅ The man who helped me.

2. Unnecessary repetition

   • ❌ The book that which I read.

   • ✅ The book that I read.

3. Using commas incorrectly

   • ❌ The car, that I bought last week, is fast.

   • ✅ The car that I bought last week is fast.

4. Omitting the pronoun when it’s needed

   • ❌ The man helped me was kind.

   • ✅ The man who helped me was kind.

Combining Sentences with Adjective Clauses

Adjective clauses make writing smoother by connecting ideas:

• Two sentences:

  • I met a woman. She works at the embassy.

  • Combined: I met a woman who works at the embassy.

• Two sentences:

  • I bought a phone. It has a great camera.

  • Combined: I bought a phone that has a great camera.

This makes sentences more concise and natural.

Advanced Tips

1. Use “whose” for possession even with objects:

   • I stayed at a hotel whose rooms were spacious.

2. Use “preposition + whom/which” in formal writing:

   • The colleague with whom I work is from Japan.

   • The project for which we applied was approved.

   • (In informal English: “The colleague I work with” or “The project we applied for.”)

3. Avoid using “that” after prepositions

   • ❌ The person with that I spoke.

   • ✅ The person with whom I spoke.

Practice Exercise

Identify the adjective clauses and the nouns they modify:

1. The house that Jack built is still standing.

2. The movie which won the award was directed by Nolan.

3. The teacher who loves literature gave us a book.

4. The day when we first met is unforgettable.

5. The store where I bought this jacket is near the station.

Answers:

1. that Jack built → modifies house

2. which won the award → modifies movie

3. who loves literature → modifies teacher

4. when we first met → modifies day

5. where I bought this jacket → modifies store

Summary

Conclusion

Adjective (relative) clauses make English richer and more precise. They help connect ideas, describe nouns more clearly, and make sentences flow naturally. By mastering when to use who, which, that, or where, and understanding punctuation rules, you’ll be able to write and speak with clarity and sophistication.

Whether you’re writing essays, reports, or stories, adjective clauses are a key tool for expressing complex thoughts simply and elegantly.

What is an adjective (relative) clause?

An adjective clause—often called a relative clause—is a dependent clause that modifies a noun or pronoun. It begins with a relative pronoun (such as who, whom, whose, which, that) or a relative adverb (such as where, when, why) and contains a subject and a verb. Its job is the same as an adjective’s: to add information or identify which person, thing, place, or time you mean. Example: “The book that I borrowed is fantastic.”

How do adjective clauses differ from adjective phrases?

An adjective clause has both a subject and a verb (e.g., “who lives next door”). An adjective phrase does not contain a finite verb (e.g., “living next door”). Clauses can provide more precise information and can include tense and agreement; phrases are more compact but sometimes less specific.

Which relative pronouns are used and when?

Use who for people as a subject (“the teacher who explains clearly”), whom for people as an object in formal style (“the colleague whom you called”), whose for possession (“the artist whose work won”), which for things/animals (“the laptop which crashed”), and that for people, things, or animals in restrictive clauses (“the team that won”).

What is the difference between restrictive and non-restrictive adjective clauses?

A restrictive (defining) clause is essential to identify the noun; it is not set off by commas: “Students who submit late lose points.” A non-restrictive (non-defining) clause adds extra, nonessential information and is enclosed in commas: “My sister, who lives in Manila, is visiting.” Removing a restrictive clause changes which person/thing you mean; removing a non-restrictive clause leaves the core meaning intact.

When should I use “that” versus “which”?

In careful or formal writing, use that for restrictive clauses and which for non-restrictive clauses (with commas). Examples: “The policy that applies here is new.” vs. “The policy, which was updated yesterday, applies here.” In everyday speech, some speakers use which restrictively, but sticking to the distinction improves clarity.

Can I omit the relative pronoun?

Yes, but only when the pronoun is the object of the clause. “The movie (that) I watched” and “The person (whom) we met” are both acceptable with omission. Do not omit the pronoun when it is the subject: “The engineer who designed the bridge…” (You cannot say “The engineer designed the bridge…” as a clause without who.)

What are relative adverbs “where,” “when,” and “why” used for?

Use where to modify places (“the café where we met”), when for times (“the year when I graduated”), and why for reasons (“the reason why she left”). In formal style, you can often replace them with “in which,” “on which,” or “for which”: “the year in which I graduated.”

What is the correct punctuation for adjective clauses?

Do not use commas with restrictive clauses; do use commas to set off non-restrictive clauses. Misplacing commas can reverse the meaning. Compare: “Employees who fail the test must retake it” (only some employees) vs. “Employees, who fail the test, must retake it” (implies all employees fail).

How do I decide between “who” and “whom” in modern usage?

Who functions as a subject; whom functions as an object or after a preposition. Test by substituting he/she (subject) or him/her (object). Formal style: “the client to whom I spoke.” Informal but common: “the client who I spoke to.” Using whom remains the safest choice after prepositions in formal writing.

Can an adjective clause modify a pronoun?

Yes: “Those who arrive early will be seated first.” The clause modifies the pronoun those by identifying a subset.

Is “whose” only for people?

No. Whose can show possession for people, animals, or things: “a company whose values we respect,” “a city whose skyline is iconic.” This usage is standard and widely accepted.

Can I place prepositions before or after the relative pronoun?

In formal style, place the preposition before whom/which: “the principle on which the method rests,” “the colleague with whom I collaborate.” In everyday English, stranding the preposition at the end is natural: “the colleague I collaborate with.” Do not use a preposition directly before that: avoid “the person to that I wrote.”

What are common mistakes with adjective clauses?

Frequent errors include using which for people (“the man which helped me”), doubling pronouns (“the book that which I read”), misusing commas around restrictive clauses, and omitting necessary subjects (“the scientist discovered the cure was brilliant” instead of “the scientist who discovered the cure…”). Another mistake is mismatched reference—ensure the clause clearly and logically modifies the intended noun.

How can adjective clauses improve sentence variety?

They allow you to combine choppy sentences and avoid repetition. Instead of “I met a woman. She works at the embassy,” write “I met a woman who works at the embassy.” The clause integrates detail smoothly, enhancing cohesion and concision.

When should I prefer an adjective phrase or appositive instead?

If brevity is your priority and the tense is not crucial, an adjective phrase may suffice: “the students arriving late.” When renaming a noun with extra information, an appositive can be ideal: “Marie Curie, a pioneering physicist, won two Nobel Prizes.” Choose the structure that matches your emphasis and formality.

Do adjective clauses affect subject–verb agreement?

Agreement depends on the head noun, not on intervening clauses. Example: “The list of items that are required is on the desk.” Although items is plural inside the clause, the main subject is list (singular), so the main verb is singular.

Can I use “that” in non-restrictive clauses?

Standard usage avoids that in non-restrictive clauses. Use which instead and add commas: “The report, which I finalized yesterday, will be presented tomorrow.” Reserve that for essential (restrictive) information.

How do I choose between “where” and “which…in which”?

Where is more natural for everyday writing: “the house where I grew up.” In formal contexts or when the head noun is abstract (e.g., situation, case, context), “in which” may be clearer: “the scenario in which costs decrease.” Avoid using where when the head noun is not a place unless idiomatic: prefer “the reason why,” not “the reason where.”

How can I avoid misplaced or ambiguous relative clauses?

Place the adjective clause immediately after the noun it modifies. Ambiguity arises when another noun sits closer to the clause. Compare: “I spoke with the manager of the branch who approved the refund” (unclear) vs. “I spoke with the branch manager who approved the refund” (clear) or “I spoke with the manager of the branch that approved the refund.”

Are there style tips for formal academic or business writing?

Prefer explicit, non-ambiguous structures; maintain the that/which distinction; use whom after prepositions; avoid stranded prepositions in highly formal documents; and ensure non-restrictive clauses add value rather than clutter. Vary structures to balance clarity and flow.

Can adjective clauses be reduced?

Yes. When the relative pronoun is the subject and the verb is in an active, continuous, or simple form, you can often reduce to a participial phrase: “Students who arrive late” → “Students arriving late.” For passive meaning: “documents that are required” → “documents required.” Use reductions when they do not create ambiguity.

What drills help me master adjective clauses quickly?

Try three steps: (1) Identify the head noun; (2) Choose the correct relative word based on person/thing, role (subject/object), and possession; (3) Decide if the information is essential (no commas) or extra (commas). Practice combining two simple sentences into one with a relative clause and then attempt reductions for concision.

Can I stack or nest adjective clauses?

Yes, but use sparingly to preserve readability. Example: “The researcher who led the team published data which the journal, which is well-regarded, verified.” In practice, rewrite or split the sentence if comprehension suffers.

What are some quick before-you-publish checks?

Confirm that (a) the clause directly follows the noun it modifies; (b) commas match the clause type; (c) the chosen relative pronoun fits its grammatical role; (d) reductions have not changed meaning; and (e) the sentence remains concise and fluid.

Can adjective clauses appear after indefinite pronouns like “something” or “anything”?

Yes: “Is there anything that I can do?” “Choose something which suits your needs.” Omission is also common when the pronoun is object: “Is there anything (that) you need?”

What is the best way to teach or learn adjective clauses?

Start with clear contrasts between restrictive and non-restrictive clauses using color-coded commas. Drill pronoun choice with substitution tests (he/him). Combine sentence pairs daily for two weeks, then move to reductions. Finally, peer-edit short paragraphs focusing only on clause placement and punctuation.

Can I use “that” after superlatives and pronouns like “all,” “everything,” “the only”?

Yes, that is common after superlatives and certain determiners: “the best decision that we made,” “all the data that we collected,” “the only route that works.” Using which here is possible but less idiomatic in many dialects.

Why do editors care so much about comma placement with relative clauses?

Because commas signal whether information is essential. Misplaced commas can alter scope, create unintended generalizations, or imply facts that are not true. Accurate comma use preserves meaning, tone, and legal or technical precision.

Can I rewrite adjective clauses to make sentences more direct?

Absolutely. Convert non-restrictive clauses into separate sentences for emphasis (“Our proposal—which exceeded targets—was approved” → “Our proposal exceeded targets. It was approved.”). Convert restrictive clauses into compound modifiers or participles when natural (“policies that conflict” → “conflicting policies”). Choose the clearest form for your audience.