1. Two types of relative clauses: Non-Defining   Extra information about a noun in a sentence The new Woody Allen film, which I saw last week, is very good.   Use commas   Always use a relative pronoun: who/whom,which whose, where, when Defining   Essential information about a noun in a sentence You’re the man (that) I saw last week.   No commas   Can omit pronoun if it is not the SUBJECT of the relative clause   That (informal) can replace which / who/ when / why but not where, whose or whom

2. Defining relative clauses = No commas A defining relative clause identifies which person or thing we mean exactly. It cannot be left out of the sentence or the meaning of the sentence is incomplete : It’s the book that I read yesterday. * It’s the book. (this sentence is incomplete)

3. Defining relative clauses = No commas  You can omit the pronoun if it is the OBJECT of the relative clause (if there is a SUBJECT and a VERB after the relative pronoun ) It’s the book that I read yesterday  (omit) It’s the book I read yesterday. It’s the book I read yesterday. The girl who lives next door is French.  We can never omit WHOSE and WHERE

4. Non-defining relative clauses = with commas This kind of clause gives additional information about a person or thing. The sentence still makes sense without the non-defining relative clause:  My neighbour, who studies engineering, is very noisy.  My neighbour is very noisy.

5. Formal / Informal  Non-Defining relative clauses (with commas) are more common in written English because they are quite formal. In spoken English we would probably use two sentences. Compare: Elvis Presley, who has sold over one billion albums, died of prescription drug abuse. [written] with Elvis has sold over a billion albums. He died of an overdose. [spoken ]