Relative clauses give us more information about someone or something. We can use relative clauses to combine clauses without repeating information.
The couple posted a Christmas present to their daughter, who lives in South Africa.
The couple posted a Christmas present to their daughter.
Their daughter lives in South Africa.
Using a relative clause means that there is no need to repeat ‘their daughter’.
We can use relative clauses to give focus to something or someone.
This is the book which we’re reading at the moment.
We’re reading this book at the moment.
She’s the woman who I was talking about.
I was talking about the woman.
Types of relative clause
There are two types of relative clause: one type refers to a noun or noun phrase (these are defining and non-defining relative clauses) and the other type refers to a whole sentence or clause, especially in speaking.
Defining and non-defining relative clauses
Defining and non-defining relative clauses define or describe the noun (or noun phrase) that comes before them (In the examples, the relative clause is in bold, and the person or thing that is referred to is underlined.):
He’s going to show you the roomsthat are available. (that are available defines the rooms; it tells us which rooms)
Dodingson, 22, who boxed in two Olympics, will be managed by his close friend Colin McFarllan. (who boxed in two Olympics describes Dodingson; it is extra information about him)
The other type of relative clause refers to a whole sentence or stretch of language (they are sometimes called sentential relative clauses). This type of relative clause is always introduced with which. In writing we usually put a comma before which:
But I think Sean was a bit upset about that, which is understandable. (which is understandable refers to the whole clause before it [underlined]: that Sean was upset about something)
She goes to Canada and stays with her daughter, and then her daughter comes here the next year. Every other year they change places you know. Which is nice. (Which is nice refers to the whole stretch of text before it [underlined]. This is common in speaking but not in writing.)