Relative clauses are clauses that qualify a preceding noun (known as the antecedent) in a sentence, like these:
I’m looking for the man who took my pen.
He took the gold pen, which was a present from my father.
They all contain a relative pronoun, which is one of these: who, whom, which, whose, that and, in certain circumstances, what. We use them when we need to add more information about the noun to the sentence, or – to put it another way – to get more information into a sentence.
A rule (that) you don’t know you know
There are some rules about the use of relative clauses that native speakers of English will pick up and never really need to have them explained. We know, for example, that we can omit the relative pronoun in a sentence like ‘The pen that I got from my dad’, and say ‘the pen I got from my dad’; but that we can’t omit the pronoun in the sentence ‘I’m looking for the man who took my pen’ without making a nonsense of the sentence. The reason is that in the first sentence the relative pronoun is the object of the sentence – my dad (subject) gave (verb) the pen (object), whereas in the second sentence the relative pronoun is the subject of the sentence – the man (subject) took (verb) my pen (object). It is more formal, of course, to retain the relative pronoun, but we sort of know that too without needing to be told.
A rule that will set your commas straight
Rules about commas and their usage are rarely so instinctual. Funny that, isn’t it? Let me step in where instinct is loath to tread. There are two types of relative clause: a defining relative clause (or ‘restrictive’) and a non-defining (‘non-restrictive’) relative clause. Once again we’re stuck with two alternative sets of terminology which grammar books use as is their wont, but I’m going to stick with defining and non-defining as I think that they describe the way we use them more precisely.
A defining relative clause is one that defines the antecedent. Without this clause, we don’t exactly know whom or what you’re talking about:
I’m looking for the man.
What man? Who? Why are you looking for him?
I’m looking for the man who took my pen!
Oh right, that man. The clause ‘who took my pen’ tells us who the man is. You don’t set off these clauses from the rest of the sentence.
A non-defining relative clause tells us something extra about the antecedent, something very important perhaps, but not something we need to know to be sure of what it is. To put it more simply, we already know whom or what you’re talking about without this clause:
I’m looking for Gemma, who took my pen, and Boris, who took my folder.
Ah, Gemma and Boris? They’re long gone, mate. You don’t care about my pen and folder, do you, you heartless slob? I could just as easily have said:
I’m looking for Gemma and Boris.
These are non-defining relative clauses, so need commas.
Sundry rules and vexations
‘That’ can be used interchangeably with ‘which’, ‘who’ and ‘whom’. It is probably used a lot more frequently in speech, but it can sound rather informal in some sentences. ‘Whose’ shouldn’t be confused with ‘who’s’, which is a contraction of ‘who is’ or ‘who has’. Writing who apostrophe s to mean whose is another of those logical but wrong constructions that people come up with sometimes to vex grammarians, teachers and people who mark exams. Whose can be used for objects as well as things, by the way, such as in this sentence:
We had to tow the car whose owner had been imprisoned.
However, this does not apply to interrogative whose, which always refers to the possessions of a person (Whose is this?).
What is a special case – it is only used in a nominal relative clause, where the relative pronoun and the antecedent are combined in one word. If you’re having difficulty picturing that, here’s an example:
What I want is immaterial, dear.
(The thing that I want is immaterial dear)
Using what instead of which or who is wrong and should only be done humorously or when we are writing speech exactly the way it was said: ‘I’ve done me grammar homework what me teacher give us’. It was used by the Sun newspaper in the 1990s when they claimed that their campaigning had clinched the elections for the Conservatives at the expense of the Labour party: ‘It’s the Sun Wot Won it’. Their bad grammar and misspelling was quite deliberate, perhaps aimed at annoying intellectuals and school teachers, who by and large vote Labour.
Add a relative clause to each of the following sentences. Make it humorous if you wish, but be sure that you’re getting the rules right.
I fell in love with a girl.
I took all of the farm animals.
She pulled a coat out of the wardrobe.
The Queen of England likes to talk to a young man.
The park was full of the kind of people…