Use an appropriate relative pronoun
Robert's parents live in Spain, which I'm sure is amazing.
Type 1: comments on the whole main clause.
I was sitting on a chair which belonged to my grandmother.
I was sitting on a chair which belonged to my grandmother.
DEFINING. It is identifying exactly which chair it is.
Sydney which has a population of more than 3 million is Australia's largest city.
COMMAS: Sydney, which has a population of more than 3 million, is Australia's largest city.
Starbucks wants to open new stores in China. It does business all over the world.
Starbucks, which does business all over the world, wants to open new stores in China.
The book which I read last week is fascinating. You must read it, too!
Type 2: identifies something in the main clause (the book).
I know a man who played for Arsenal in the 80s.
I know a man who played for Arsenal in the 80s.
DEFINING. It is identifying the man.
My new apartment which you visited yesterday is bigger than my old one.
COMMAS: My new apartment, which you visited yesterday, is bigger than my old one.
Scientists are working with stem cells. Stem cells will revolutionize medicine.
Scientists are working with stem cells, which will revolutionize medicine.
I saw the film "Casablanca", which won an Oscar in 1942.
Type 3: gives extra, non-essential information about something in the main clause (the film "Casablanca").
I love New Zealand whose landscapes are simply spectacular.
I love New Zealand, whose landscapes are simply spectacular.
NON-DEFINING. it is giving extra information about New Zealand.
The politician who visited our neighbourhood wants to make it safer for children to play outside.
NO COMMAS
Last week, Jim Taylor interviewed Sally Thompson. She is my neighbour.
Last week, Jim Taylor interviewed Sally Thompson, who is my neighbour.
I saw the woman whose daughter won the lottery yesterday. She looked very happy!
Type 2: identifies something in the main clause (the woman).
The King of Spain who loves sailing participated in the Olympics.
The King of Spain, who loves sailing, participated in the Olympics.
NON-DEFINING. It is giving more information about the King of Spain.
Last week, I visited Aunt Mary who invited me to stay with her for a while.
COMMAS: Last week, I visited Aunt Mary, who invited me to stay with her for a while.
I was told the story by a girl. I visited her in an orphanage.
I was told the story by a girl who I visited in an orphanage.
That's my cousin Sandra, whose job as a hotel manager gives her many headaches.
Type 3: gives extra, non-essential information about something in the main clause (Sandra).
The king of England who created the Anglican Church was Henry VIII.
The king of England who created the Anglican Church was Henry VIII.
DEFINING: It is identifying which king it was.
I hate it that my teachers have given me extra homework.
NO COMMAS
Al Gore gave a long and boring speech. He won a Nobel Prize.
Al Gore, who won a Nobel Prize, gave a long and boring speech.