Defining relative clauses give essential information about the noun they describe. Without this clause, the sentence wouldn’t make complete sense.

• The person who called you is my friend.
• The book that you lent me was fascinating.
• She is the artist whose paintings we saw at the gallery.
• This is the house which Jack built.

• Do not use commas to separate the defining relative clause from the main clause.
• That can replace who or which in defining relative clauses.
• Example: The car that he drives is new. (instead of “which”)

Non-defining relative clauses add extra information about the noun they describe. This information is not essential for the sentence to make sense.

• My brother, who lives in New York, is coming to visit.
• The Eiffel Tower, which is in Paris, is a famous landmark.
• Mr. Johnson, whose son is my classmate, is a lawyer.

• Always use commas to separate the non-defining relative clause from the main clause.
• Non-defining relative clauses cannot be introduced by that.
• The pronoun cannot be omitted in non-defining relative clauses.

• Defining: Essential information, no commas.
• Non-defining: Additional information, use commas.

• The man who stole my car has been arrested.
• The movie that we watched last night was thrilling.

• My neighbor, who is a retired teacher, enjoys gardening.
• London, which is the capital of England, is a very old city.