Read about using non-defining relative clauses below. Then, when you are ready, try these relative clauses practice exercises.
Non-defining relative clauses
We use non-defining relative clauses to give extra information about something - either the previous noun (use who, which, whose, whom, when or where to add the information), or all of the previous information (use which). For more information about words like which and whom, look at the relative pronouns page).
This is a photo of my friend Sarah, who got married in April.
(who = Sarah)
I've got a job in London, where I now live.
(where = in London)
Agatha Christie, whose books have been translated into many languages, died in 1976.
(whose books = her books)
I've spent a lot of time in the garden this month, which was nice.
(which = spending time in the garden, not the month)
Last night my sister ate a steak, which was very unusual.
(which = my sister eating a steak, not the steak - maybe she's vegetarian!)
Non-defining relative clauses are different from defining relative clauses. In the first sentence below, the comma (,) shows us that who work very hard is extra information - if we take out this information, the listener will still understand which teachers we are talking about. In the second sentence there is no comma - who work very hard is necessary to the meaning of the sentence because it explains which teachers we are talking about. Non-defining relative clauses need commas (,) around them, while defining relative clauses don't. Non-defining relative clauses are also less common in informal, spoken English.
Teachers, who work very hard, should get paid more.
(non-defining relative clause: all teachers should get more money, they all work hard)
Teachers who work very hard should get paid more.
(defining relative clause: only the hard-working teachers should get paid more, the lazy ones shouldn't)
Defining or non-defining?
Using a defining or non-defining relative clause (RC) can change the meaning of the sentence (as in the teachers examples above). In addition, the rules about who, which and that are different..
1. Defining RCs can use that instead of which/who. Non-defining RCs never use that.
The artist who/that sang "Holiday" in the 1980s is still making music.
(Defining RC. The information about the song helps us to know which singer we are talking about We can say who or that.)
Madonna, who sang "Holiday" in the 1980s, is still making music.
(Non-defining RC. We know who Madonna is, so the information about the song isn't necessary. We can't say that.)
2. Defining RCs don't always need who or which. Non-defining RCs always need a wh- word.
That's the man who I'm going to marry.
That's the man I'm going to marry.
(Defining RC. We don't need the word who when it's the object of the verb).
This is Andrew, who I'm going to marry.
(Non-defining RC. Who is always necessary.)
Now try these relative clauses practice exercises.