Relative Clauses: defining and non-defining

Defining Clauses

Non-defining Clauses

VS

My sister who lives in LA is an actress.

My sister, who lives in LA, is an actress.

NECESSARY INFORMATION which helps us distinguish what or who we're talking about.

EXTRA INFORMATION which isn't vital to understanding what or who we're talking about.

COMMAS ARE MANDATORY: This painting, which was painted in 1962, is worth $2 million.

NO COMMAS: Here's the church where I got married.

YOU CAN USE "that" TO REPLACE "which" OR "who": It's a book that talks about music. He's the man that works with me.

USING "that" IS NOT OKAY

You can OMIT the RELATIVE PRONOUN when the MAIN CLAUSE has a DIFFERENT SUBJECT from the RELATIVE CLAUSE:He's the man I married. This is the camera Moussa bought last year. Do you like the song I wrote? That's the reason I didn't come to class.

OMISSION: IMPOSSIBLE

PS: "where" AND "whose" CAN NEVER BE OMITTED.