Relative Clauses

Overview

A relative clause gives extra information about a noun in a sentence. It begins with a relative pronoun (who, which, that, where, when, whose) and acts like an adjective — it tells us which person or thing we are talking about.

The woman who lives next door is a doctor.

The relative clause "who lives next door" tells us which woman.

Relative Pronouns

Two Types of Relative Clauses

1. Defining Relative Clauses (Essential Information)

These tell us which person or thing we mean. Without the clause, the sentence is incomplete or unclear.

• The students who passed the exam will receive certificates.
• I need a phone that has a good camera.
• This is the restaurant where we had dinner.

Rules for defining clauses:

• No commas around the clause.
• That can replace who/which.
• The relative pronoun can be omitted when it is the object of the clause.

2. Non-Defining Relative Clauses (Extra Information)

These add extra, non-essential information. The sentence is complete without them.

• My sister, who lives in London, is visiting us next week.
• The Eiffel Tower, which was built in 1889, is in Paris.
• We visited Rome, where we ate amazing pasta.

Rules for non-defining clauses:

• Commas are required before and after the clause.
• That CANNOT be used — only who, which, where, when, whose.
• The relative pronoun cannot be omitted.

Defining vs. Non-Defining: Side by Side

Compare:

• My brother who lives in Paris is a chef. (Defining — I have more than one brother; this specifies which one.)
• My brother, who lives in Paris, is a chef. (Non-defining — I have one brother; the Paris detail is bonus info.)

When You Can Omit the Relative Pronoun

In defining clauses, you can omit the pronoun when it is the object of the relative clause:

Object — can omit:

• The film (that/which) I watched last night was great. (I = subject, film = object)
• The person (who/that) she married is very kind. (she = subject, person = object)

Subject — cannot omit:

• The man who called you is here. (who = subject of "called" — must keep it)
• The bus that goes to the airport is number 47. (that = subject of "goes" — must keep it)

Test: If there is already a subject after the pronoun, it's an object pronoun and can be dropped. If the pronoun IS the subject, it must stay.

Whose (Possession)

Whose replaces possessive words (his, her, its, their):

• I know a woman. Her daughter is a pilot.
• → I know a woman whose daughter is a pilot.

More examples:

• The man whose car was stolen called the police.
• That's the company whose products we use.
• The house whose roof was damaged has been repaired.

Whose works for people and things (though "of which" is sometimes used for things in formal writing).

Where, When, and Why

Where (places)

• This is the park where we used to play.
• The town where I grew up is very small.

Alternative with preposition: The park in which we used to play. (more formal)

When (times)

• I'll never forget the moment when I heard the news.
• Summer is the time when most people go on holiday.

Alternative: The moment (that / in which) I heard the news.

Why (reasons)

• The reason why she left is unknown.
• That's the reason why I'm late.

Alternative: The reason (that) she left is unknown. ("Why" and "that" are both optional here.)

Prepositions in Relative Clauses

Prepositions can go at the end of the clause (informal) or before the pronoun (formal):

In everyday English, the informal style (preposition at the end) is much more common.

Relative Clauses with Quantifiers

You can combine relative clauses with words like some, many, both, all, none, most:

• She has three sons, all of whom are doctors.
• He wrote ten books, most of which are bestsellers.
• There were 30 students, none of whom passed the exam.

Structure: quantifier + of whom/which

Common Mistakes

Mistake 1: Using "that" in non-defining clauses

• Wrong: Paris, that is the capital of France, is beautiful.
• Correct: Paris, which is the capital of France, is beautiful.

Mistake 2: Forgetting commas in non-defining clauses

• Wrong: My mother who is 60 still works full time.
• Correct: My mother, who is 60, still works full time.

Mistake 3: Using "what" instead of "that/which"

• Wrong: The thing what I like most is the garden.
• Correct: The thing that I like most is the garden.
• (Note: "what" = "the thing that" and cannot follow a noun.)

Mistake 4: Repeating the pronoun

• Wrong: The woman who she called me is my aunt.
• Correct: The woman who called me is my aunt.

Mistake 5: Using "who" for things

• Wrong: The car who is parked outside...
• Correct: The car which/that is parked outside...

Mistake 6: Wrong word order with prepositions

• Wrong: The person to who I spoke...
• Correct: The person to whom I spoke... OR The person who I spoke to...

Quick Reference

Practice Tips

1. Combine sentences: Take two simple sentences and join them with a relative pronoun. "I have a friend. She speaks five languages." → "I have a friend who speaks five languages."
2. Add non-defining clauses to facts: "The Amazon River, which flows through Brazil, is the largest river by volume."
3. Practice omitting pronouns: Write sentences where the pronoun is the object and try reading them without it.
4. Use "whose" in descriptions: Describe people by their possessions — "I know someone whose collection of stamps is enormous."
5. Read news articles and underline every relative clause you find. Identify whether it is defining or non-defining.