Joining Sentences Together
Relative clauses let you add information to a noun without starting a new sentence. They make your English sound more fluent and sophisticated. They start with relative pronouns.
WHO — people
the woman who called
the man who lives next door
the man who lives next door
WHICH — things/animals
the book which I read
the car which broke down
the car which broke down
THAT — people or things
the film that won the award
the person that helped me
the person that helped me
WHERE — places
the city where I was born
the hotel where we stayed
the hotel where we stayed
WHOSE — possession
the student whose work was best
the man whose car was stolen
the man whose car was stolen
Defining vs Non-defining
Defining — no commas — essential information
The man who lives next door is a doctor.
Without “who lives next door” you don’t know WHICH man. Essential information → no commas → can use that.
Non-defining — commas — extra information
My brother, who lives in London, is a doctor.
You already know which brother (I only have one). Extra info → commas → NEVER use that here.
Examples
The woman who interviewed me was very friendly.
who = person
The book which/that I recommended is out of stock.
which/that = thing
Paris is a city where fashion matters.
where = place
She’s the student whose essay won the prize.
whose = possession
💡 Memory Hack
The comma test
Try removing the relative clause. If the sentence still makes clear sense and refers to the same specific thing → it’s non-defining (add commas, no that). If removing it makes the sentence vague (which person? which thing?) → it’s defining (no commas, that is OK). “My car, which is red, is fast” → remove “which is red” → still clear (my car). Non-defining. “The car that is red is mine” → remove → “The car is mine” — which car? Defining.