English · Chapter 11

Relative Clauses: Defining and Non-Defining

Relative clauses allow you to combine information elegantly — distinguishing between the two types and knowing which pronouns to use are hallmarks of advanced English proficiency.

What Do Relative Clauses Do?

A relative clause is a type of subordinate clause that modifies a noun (called the antecedent). It answers the question "Which one?" or "What kind?" or adds extra information about the noun. Relative clauses are introduced by relative pronouns (who, which, that, whose, whom) or relative adverbs (where, when, why).

"The woman who lives next door is a doctor." (Which woman? The one who lives next door.)
"Paris, which is the capital of France, attracts millions of tourists." (Extra info about Paris.)

Relative Pronouns: Full Reference

Pronoun	Refers to	Used in	Example
who	People	Both types	The teacher who taught me Spanish was brilliant.
that	People or things	Defining only	The book that changed my life was by Orwell.
which	Things, animals, ideas	Both types	The report, which took three months, was excellent.
whom	People (object position)	Formal English	The professor whom I admire most retired last year.
whose	Possession (people/things)	Both types	The student whose essay won the prize is my friend.
where	Places	Both types	The city where I grew up has changed enormously.
when	Times	Both types	I remember the day when we first met.
why	Reasons	Defining only	That's the reason why she left.

Defining (Restrictive) Relative Clauses

A defining relative clause identifies which person or thing we are talking about. Without it, the sentence loses its essential meaning — we would not know which specific person or thing is being referred to. Defining clauses are written without commas.

    Key features of defining relative clauses:

    — No commas around the clause

    — That can replace who or which

    — The relative pronoun can be omitted when it is the object of the clause

    — The information is essential — removing it changes the meaning entirely

With who (subject position):
— "The man who called you is my brother." (Identifies which man.)
— "Students who miss three classes will fail the course."

With that (people or things):
— "The car that I bought last year is already broken."
— "The woman that won the prize is from Argentina."

With which (things):
— "The film which we saw last night was disappointing."

Omitting the pronoun (object position):
— "The book (that/which) I read was fascinating." (pronoun is optional — it's the object)
— "The man (who/that) she married is a surgeon." (she married him — object)
— Compare: "The man who called" — cannot omit (who is the subject)

When Can You Omit the Relative Pronoun?

    You can omit the relative pronoun only when it is the object of the relative clause — when there is already another noun/pronoun acting as the subject after the relative pronoun.

    "The film (that) I loved" — I is the subject; that is the object → can omit

    "The film that won the prize" — that is the subject → cannot omit

Non-Defining (Non-Restrictive) Relative Clauses

A non-defining relative clause adds extra, supplementary information about a noun that is already fully identified. The information in the clause is additional, not essential — you could remove it and the sentence would still make complete sense. Non-defining clauses are always enclosed by commas (or a comma and a period).

    Key features of non-defining relative clauses:

    — Always use commas (or dashes) to separate the clause

    — That CANNOT be used — use who or which only

    — The relative pronoun can NEVER be omitted

    — The information is additional — removing it does not change the core meaning

— "My brother, who lives in London, is visiting next week."
(We already know who my brother is — the clause adds information.)

— "Shakespeare, who was born in Stratford-upon-Avon, is England's greatest playwright."

— "The Eiffel Tower, which was built in 1889, attracts seven million visitors a year."

— "His latest novel, which took him six years to write, has already sold a million copies."

WRONG: "My brother, that lives in London, is visiting." (Cannot use "that" in non-defining clauses.)
WRONG: "My brother, lives in London, is visiting." (Cannot omit pronoun in non-defining clauses.)

Defining vs. Non-Defining: The Comma Test

The presence or absence of commas is not a stylistic choice — it completely changes the meaning of the sentence.

Defining (no commas):
"My sister who lives in Paris is an architect."
(I have more than one sister. The one in Paris is an architect.)

Non-defining (commas):
"My sister, who lives in Paris, is an architect."
(I have one sister. She lives in Paris. She is an architect — all three facts.)

Whose: Possession in Relative Clauses

Whose functions as a possessive relative pronoun for both people and things. It replaces "his/her/its/their" + noun.

— "The student whose essay won the prize is in my class."
(= the student; her essay won the prize)
— "We bought a house whose garden overlooks the sea."
(= a house; its garden overlooks the sea)
— "The company, whose CEO resigned last month, is in financial trouble."

Whom: Formal Object Position

Whom is the object form of who. It is used in formal written English when the relative pronoun is the object of the clause. In informal English, who or omission is preferred.

Formal: "The professor whom I most admire won the Nobel Prize."
Informal: "The professor who/that I most admire won the Nobel Prize."
Most informal: "The professor I most admire won the Nobel Prize." (omitted)

Formal: "The candidates from whom we heard were impressive."
(Note: preposition before whom in very formal English)

Where, When, Why as Relative Adverbs

Where (places):
— "The village where I was born has fewer than 200 people."
— "This is the office where the decision was made."

When (times):
— "I'll never forget the day when you proposed."
— "There are moments when silence is the best answer."

Why (reasons):
— "That's the main reason why I left."
— "I don't understand the reason why this keeps happening."

Quantifying Relative Clauses

These clauses use expressions of quantity + of whom / of which to give information about part of a group.

— "There were 30 applicants, most of whom had no experience."
— "She has written five novels, two of which have been adapted into films."
— "The committee has twelve members, none of whom voted in favour."
— "He sent ten emails, only one of which received a reply."

Reduced Relative Clauses

Relative clauses can often be shortened by removing the relative pronoun and be, leaving just a participle phrase. This creates more concise, formal writing.

Full Relative Clause	Reduced Form
The man who is sitting by the door is my uncle.	The man sitting by the door is my uncle.
The documents that were signed yesterday are ready.	The documents signed yesterday are ready.
Anyone who wishes to attend should register.	Anyone wishing to attend should register.
The letter that was sent last week arrived today.	The letter sent last week arrived today.

Prepositions in Relative Clauses

When the relative pronoun is the object of a preposition, the preposition can go at the end (informal) or before the pronoun (formal).

Informal: "The company that I work for is expanding."
Formal: "The company for which I work is expanding."

Informal: "The friend who I was talking to is a journalist."
Formal: "The friend to whom I was talking is a journalist."

Chapter Summary

Defining relative clauses identify which specific person or thing is meant; they use no commas, can use that, and allow pronoun omission when the pronoun is the object.
Non-defining relative clauses add supplementary information about an already-identified noun; they require commas, cannot use that, and the pronoun can never be omitted.
The comma distinction is not stylistic — "My sister who lives in Paris" (one of several sisters) vs. "My sister, who lives in Paris," (only one sister) carry completely different meanings.
Who is used for people, which for things, that for both (defining only), whose for possession, and whom for people in object position (formal).
Relative adverbs where, when, and why replace prepositional phrases referring to place, time, and reason.
Quantifying relative clauses (most of whom, none of which, two of which) are used to describe part of a group mentioned previously.
Reduced relative clauses (removing pronoun + be, leaving a participle) create concise, formal prose — essential for academic and professional writing.