Defining and Non-Defining Relative Clauses

He gave me the letter, ... was in a blue envelope. 

He gave me the letter, ... I read immediately. 

Stratford-on-Avon, ... many people have written about, is Shakespeare's birthplace. 

We stopped at the museum, ... we had never visited before.

I've just come back from London, ... John lives..

Yesterday I met a woman named Susan, ... husband works in London.

They are the people..... bought our house.

Here are some cells ... have been affected

They should give the money to somebody ... they think needs the treatment most.

She’s now playing a woman ... son was killed in the First World War.

They’re the people ... bought our house. 

They’re the people ... she met at Jon’s party

In defining clauses we ....

In non defining clauses ....