Relative pronoun clauses: the essentials

What is a relative clause?

The dog which howled all night

Relative clauses are a way to define or add information to a noun in a sentence.
So, for example, in
The dog which howled all night and kept me awake
The noun, dog, is rendered unique among millions of dogs because only this one howled and caused me a sleepless night. The pronoun which refers back to the noun dog and dog is the subject of the verb howl (the dog howled). We can make the same idea in English with two sentences like this:

The dog howled all night
The dog kept me awake

but it is easier and clearer to use a relative pronoun to link the ideas.

Here is another example of a slightly different sort of relative clause:
The White House, that stands on Pennsylvania Avenue, is a huge building
Here, too, we can make two sentences:

The White House stands on Pennsylvania Avenue
The White House is a huge building

The situation is slightly different because we already know that The White House is unique (it's the name of a particular building) so the fact that it stands on Pennsylvania Avenue is just extra information. The fact that it stands there does not define the building, it just adds data
Look where the commas appear and you will see that the clause is divided from the rest of the sentence.
That's important, as we shall see.

Five types of clause

We use five pronouns to make relative clauses

pronoun	use	examples
who	subject or object pronoun for people	The students who had the party are now living over there.
which	subject or object pronoun for animals and things	What have you done with the book which I lent you? The dog, which was lying in the dark, suddenly barked at me.
which	referring to a whole clause or previously mentioned idea (only which can do this)	They fell in love and got married the following month which surprised everyone.
whom	object pronoun only for people (formal)	Melissa, whom I met at the party, invited me.
whose	possession	Do you know the man whose car is parked on the corner?
that	subject or object pronoun for people, animals and things (who or which are also possible)	I don’t like the book that he gave you. He’s the man that I saw. The kids that came with me had lunch on the train.

Defining and non-defining relative clauses

Here are four sentences to compare:

What's the difference in meaning between these pairs of sentences? Try saying the sentences aloud to get a feel for the meaning.
Click here when you have an answer.

At the first meeting, which was held yesterday, the chair invited comments from everyone.
At the first meeting which was held yesterday the chair invited comments from everyone.
The kids, who came with me, had lunch on the train.
The kids who came with me had lunch on the train.

Sentence 1: contains a non-defining relative clause. The fact that the meeting was held yesterday is additional information which can be ignored because the sentence makes sense without it.
We can put the relative clause in brackets with no change in meaning: At the first meeting (which was held yesterday) the chair invited comments from everyone.
Sentence 2: contains a defining relative clause. We are only talking about the first meeting which was held yesterday. Other meetings were held yesterday but we are only concerned with the first of these.
Sentence 3: contains a non-defining relative clause. The only kids in question are those who came with me. All the kids had lunch on the train and the extra information that they came with me is additional (and it could appear in brackets, like this).
Sentence 4: contains a defining relative clause. There were other kids (who came alone or with someone else) who had no lunch / had lunch somewhere else. I only know that the kids who came with me had lunch.

Now look at these four sentences.

Sentence	Comment
The Statue of Liberty, which stands in New York, is well known.	The clause which stands in New York is between the commas because it is simply adding information concerning the location of something known to us all. There is only one Statue of Liberty so we do not need to define it.
The Statue of Liberty which stands in New York is well known.	There is only one such statue so to omit the commas would be wrong. You cannot define that which is already unique.
The statue of Gandhi which stands in Tavistock Square is well known.	There are many statues of Gandhi around the world so to define a particular one by where it is is acceptable.
The statue of Gandhi, which stands in Tavistock Square, is well known.	This is also acceptable. Here we are talking about a statue of Gandhi but adding information to say where it is, not defining it.

Subject or Object?

It's important to know whether the relative pronoun is acting as the subject or the object of the verb.
The subject of a verb is the person or thing that does the action.
The object of the verb is the person or thing that receives the action.
Like this:

Subject	Verb	Object
The horse	threw	the rider
Mary	made	soup

What's the relative pronoun doing in the following examples? Look at the underlined clauses and decide if they refer to the subject or object of the verb phrase.
Click when you have an answer.

The man who bought the tickets really is just being generous
The tickets, which hopefully will allow us entry, are very welcome
The man that we thanked seemed genuinely surprised
The tickets which he bought were quite expensive
Only the senior doorman, who we gave the tickets to, noticed that they were fakes

Here are the answers:

The man who bought the tickets really is just being generous – subject – the pronoun who is followed by verb phrase (bought the tickets)
We can re-phrase the first part of the sentence as
The man bought the tickets (Subject – Verb – Object)
The tickets, which hopefully will allow us entry, are very welcome – subject again – which is followed by the verb phrase hopefully will allow us
We can re-phrase the first part of the sentence as
The tickets will hopefully allow us entry (Subject – Verb – Object)
The man that we thanked seemed genuinely surprised – object – that is the object of we thanked
We can re-phrase the first part of the sentence as
We thanked the man (Subject – Verb – Object)
The tickets which he bought were quite expensive – object – which is the object of he bought
We can re-phrase the first part of the sentence as
He bought the tickets (Subject – Verb – Object)
Only the senior doorman, who we gave the tickets to, noticed that they were fakes – indirect object after preposition to
We can re-phrase the first part of the sentence as
We gave the tickets to the senior doorman (Subject – Verb – Direct Object – Indirect Object)

A simple rule to tell students is:
If the relative pronoun is followed directly by a verb phrase, it’s the subject.
So, in The man who just bought the car, the relative pronoun, who, is followed directly by the verb phrase, just bought. This means that the relative pronoun stands for the subject of the verb.
If the pronoun is not followed by a verb phrase (but by a noun phrase or pronoun) it is the object.
So, in The book which she bought was a first edition, the relative pronoun, which, is followed by a pronoun, she, so it cannot be the subject of the verb. The relative pronoun stands for the object of the verb.

Omitting the pronoun

Sometimes, we can leave out the pronoun altogether so instead of:
The house which he bought
we can have:
    The house he bought
and instead of:
    The woman who(m) you saw in Margate
we can have
    The woman you saw in Margate

In which of these sentences can you omit the relative pronoun?

The book which I read yesterday is on the shelf
The man who gave you the money is very generous
The children who came late were punished
The water which he drank made him unwell
The spider, which he killed, was quite harmless

Can you see what the rule is?
Click here when you have an answer.

In Sentences b, c and e we cannot leave out the pronoun because that makes unacceptable sentences:
    *The man gave you the money is very generous
    *The children came late were punished
    *The spider, he killed, was quite harmless
In sentences a and d we can leave out the pronoun and make acceptable sentences:
    The book I read yesterday is on the shelf
    The water he drank made him unwell

Rule 1 is: If the relative pronoun refers to the subject of the verb we must use it.
In sentences b and c, the relative pronoun is the subject of the verb because we can re-phrase them like this:
    The man gave you the money
    The children came late

Rule 2 is: Object pronouns can be dropped ...
In sentences a and d, the relative pronoun is the object of the verb because we can re-phrase them like this:
I read the book
The man drank the water

... but only in defining relative clauses
In sentence d, we have commas after the spider and killed. We know that it is a non-defining relative clause and the commas could be replaced by brackets with the same meaning.:
The spider (which he killed) was quite harmless

Is it possible to omit whose?
No.
We can have:
The man whose tickets we stole
but not
*The man tickets we stole

	Using that
The man that she met

We can replace who, whom and which with the pronoun that in many cases but there is a rule here, too.

In which of these sentences can that be used as the relative pronoun instead of who, whom or which?
What's the rule? Click here when you have an answer.

The table, which was too expensive for me anyway, had been sold
The bus which I took to the game was 10 minutes late
The man who(m) she married was quite rich
Mary, who is Fred's sister, is a concert pianist

In sentences b and c we can replace which and who(m) with that, so we have the sentences:
     The bus that I took to the game was 10 minutes late
    The man that she married was quite rich
In sentences a and d, be cannot use that because we get:
   *The table, that was too expensive for me anyway, had been sold
    *Mary, that is Fred's sister, is a concert pianist
The rule is:
The pronoun that can only be used in defining relative clauses and then it’s more informal.
(Some people might accept using that for the table in a non-defining clause but it is clumsy and often unacceptable to do so.)

There is a lot more to learn about relative clauses but at the initial stage of a teaching career, this is plenty. It's a complicated area and needs careful handling.

Related guides
the in-service guide	this is a more technical guide which includes all of this and much more
relative adverbs	for more on another form of relative clause using adverbs

Click for a test in this area.