I'm relearning English from scratch to build a solid foundation — Relative Clauses are where sentences start to sound sophisticated, combining two ideas into one.
What Is a Relative Clause?
A relative clause modifies a noun — it tells us which person, thing, or place we're talking about, without starting a new sentence.
The man who lives next door is a doctor.
→ "who lives next door" tells us which man
The book that I bought yesterday is really good.
→ "that I bought yesterday" identifies which book
This is the city where I was born.
→ "where I was born" specifies which city
Which Relative Pronoun to Use?
WHO
For People Only
Refers to a person — replaces he/she/they
The teacher who taught me retired last year.
WHICH
Things & Animals
Refers to things or animals — never people
The car which she drives is a Tesla.
THAT
People + Things (Defining only)
Can replace who or which in defining clauses — more informal
The person that called left a message. The app that I use every day is free.
WHERE
Places
Refers to a place — replaces "in which / at which"
This is the café where we first met.
WHEN
Time
Refers to a time expression — day, year, moment, time
I remember the day when I graduated.
WHOSE
Possession
Shows ownership — replaces his/her/its/their
The student whose essay won got a scholarship.
Defining vs Non-Defining Clauses
Type 1
Defining Clause
Essential information — removing the clause changes the meaning or leaves the sentence incomplete.
No commas · Can use "that"
The man who called you is my uncle. Without "who called you" — which man?
Type 2
Non-Defining Clause
Extra information — the sentence is still clear without it.
Commas required · Cannot use "that"
My brother, who lives in London, is visiting next week. Without the clause — still clear
Quick test: Can the reader identify the noun WITHOUT the clause?
Yes → Non-Defining (add commas) · No → Defining (no commas)
Omitting the Relative Pronoun
You CAN drop the pronoun when it acts as the Object of the clause:
The book (that) I read was amazing. → "I" = Subject, book = Object → can drop "that"
You CANNOT drop the pronoun when it acts as the Subject:
The man who called — "who" IS the subject → cannot drop it
Common Mistakes
✗
The man which called me is my boss. ("which" cannot refer to a person)
✓
The man who called me is my boss.
✗
My sister, that lives in Bangkok, is a nurse. ("that" not allowed in non-defining clauses)
✓
My sister, who lives in Bangkok, is a nurse.
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The city where I was born it is beautiful. (double pronoun — "where" already replaces "it")
✓
The city where I was born is beautiful.
Quick Reference Table
Pronoun
Used for
Example
WHO
People (subject/object)
the woman who helped me
WHOM
People (object — formal)
the man whom I met
WHICH
Things / Animals
the car which I drive
THAT
People + Things (Defining only)
the person that called
WHOSE
Possession
the student whose work was best
WHERE
Places
the place where we met
WHEN
Times
the year when I started
Practice — Combine the sentences
1. I have a friend. She speaks 5 languages.
→ I have a friend who speaks 5 languages.
2. This is the restaurant. We celebrated our anniversary there.
→ This is the restaurant where we celebrated our anniversary.
3. I read the article. You recommended it.
→ I read the article (that) you recommended. ("that" optional — "you" is the Subject)
4. The man won the race. His training was legendary.
→ The man whose training was legendary won the race.
5. 2020 was a difficult year. The pandemic started then.
→ 2020 was the year when the pandemic started.
KEY TAKEAWAY
WHO = people · WHICH = things · THAT = both (Defining only)
WHERE = places · WHEN = times · WHOSE = possession