Relative clauses

A relative clause gives extra information about nouns - how exactly does it do this? Unlike an adjective, which in English comes before the noun, relative clauses always follow the noun that they are defining or describing. In the following examples, the whole relative clause is in bold:

I enjoyed the concert that we went to last night.
The book which I'm reading comes from the library.
The people who you met at the party are all old friends of mine.
He hadn't met the man who I was talking about.

The first thing to notice from these examples is that the relative clause can come both at the end and in the middle of the sentence. The second point of interest is the type of word that can introduce a relative clause, in these instances, which, who and that - in this context these words are known as relative pronouns.
We can opt to use that where we might sometimes use which or who, as you can see from these sentences modified from the ones above:

The book that I'm reading comes from the library.
The people that you met at the party are all old friends of mine.
He hadn't met the man that I was talking about.

You may also have noticed that there is another relative clause construction that can be applied to all the above examples - the relative pronoun can be left out with no obvious change in meaning.

I enjoyed the concert we went to last night.
The book I'm reading comes from the library.
The people you met at the party are all old friends of mine.
He hadn't met the man I was talking about.

But what about the following sentences?

I can't find my notebook that contains all my addresses.
She has never met the lecturer who is leading today's seminar.
The tall man who was standing by the bar is my uncle.
The newspaper which first reported the incident is being sued.

Again, the relative clause can occupy the same positions as before, but try to take out the relative pronoun this time and compare the results. You should find that they do not produce acceptable English sentences. Can you see why?

Subject and object relative clauses

The answer is that in the first set of four sentences the relative pronoun is the object of the relative clause, like this:

I enjoyed the concert. We went to the concert last night.
The book comes from the library. I'm reading the book.
The people are all old friends of mine. You met the people at the party.
He hadn't met the man. I was talking about the man.

In each case the sentence which becomes the relative clause is shown second and adds extra information to the subject or the object of the first (main clause) sentence.
With this type of clause we can choose either to use the relative pronouns or to omit them. In fast colloquial speech, omission is the norm, whereas in written English we tend to leave them in.
In the second set of four sentences, however, the subject or the object of the main clause is the subject of the relative clause:

I can't find my notebook. My notebook contains all my addresses.
She has never met the lecturer. The lecturer is leading today's seminar.
The tall man is my uncle. The tall man was standing by the bar.
The newspaper is being sued. The newspaper first reported the incident.

In these cases we cannot leave out the relative pronoun and expect a fully coherent sentence to remain. However, as with object relative clauses we can use that instead of which or who.

She has never met the lecturer that is leading today's seminar.
The tall man that was standing by the bar is my uncle.
The newspaper that first reported the incident is being sued.

So, when you first see a relative clause it is a good idea to decide whether you are looking at subject relative clause or an object relative clause.

Reduced relative clauses

Although it is not possible to omit the relative pronoun in the subject relative clauses that we have just looked at, we can, if we want, omit an even larger piece of the relative clause and still retain a grammatically acceptable sentence. Using the examples from above, we can say:

I can't find my notebook containing all my addresses.
She has never met the lecturer leading today's seminar.
The tall man standing by the bar is my uncle.
The newspaper first reporting the incident is being sued.

This is usually referred to as a reduced relative clause and can only be applied to subject relative clauses not object relative clauses.
The most obvious feature of this type of reduced clause is that the relative pronoun is left out and the verb following the noun always ends in -ing. The second, but perhaps not quite so obvious feature is that the tense of the verb in the original relative clause is not taken into account. Note how the verb tenses varied in the original sentences:

I can't find my notebook that contains all my addresses. (Present Simple)
She has never met the lecturer who is leading today's seminar. (Present Continuous)
The tall man who was standing by the bar is my uncle. (Past Continuous)

The newspaper which first reported the incident is being sued. (Past Simple)

These -ing forms of the verb in a reduced relative clause are called non-finite verbs, that is, they are not marked in any way for tense. Here, the tense is carried only in the verb of the main clause.
So, to sum up so far, subject relative clauses cannot lose their relative pronoun, except when the whole relative clause is reduced to a non-finite -ing verb form. Object relative clauses can lose their relative pronoun, but cannot form reduced relative clauses.
Now consider the following set of sentences:

The information given in the brochure is wrong.
The criminal picked up at the airport was taken into police custody.
We saw the new play written by Tom Stoppard at the Old Vic.
The second piece played by the orchestra was very well received.

These are also examples of reduced subject relative clauses, but this time the word immediately following the noun which is being described is not an -ing type finite verb but a past participle; these are in bold.
The difference here is that those reduced relative verbs ending in -ing (looked at above) stand in for active verbs, while the past participles replace passive verbs and, as with the former type, they can replace almost any tense.
However, continuous tenses are usually replaced by being + past participle, so in the last sentence we might want to bring it into the here and now by saying: The second piece being played by the orchestra was especially commissioned. Among the possibilities for the full relative clauses for each of the above examples are:

The information which is given in the brochure is wrong.v
The criminal who was picked up at the airport was taken into police custody.
We saw the new play that was written by Tom Stoppard at the Old Vic.
The second piece which was played by the orchestra was very well received.

Defining and non-defining relative clauses

So far we have looked at subject and object relative clauses, and reduced active and passive subject relative clauses. There is one more relative clause pair that we need to consider - defining and non-defining relative clauses. Look at the following examples of each type - can you find the essential difference between them?

My sister who lives in London is married to a lawyer.
My sister, who lives in London, is married to a lawyer.

The difference in meaning is that in the first sentence I have more than one sister, whereas in the second I have only one. The relative clause in the first sentence is crucial to identifying which of my sisters I am talking about - the one in London, not the one in Manchester; this is called a defining relative clause because it singles out one thing of many. The second relative is not necessary for identifying my sister since I have only one, but is, rather, just a bit of extra information; this is called a non-defining relative clause.
In everyday life, it is fairly uncommon to use non-defining clauses if only because we are interested in giving news rather than repeating what is already known to our listener, so you are more likely to hear and see defining relative clauses. Non-defining relative clauses are generally confined to academic and similar types of text where the writer or speaker needs to demonstrate that s/he knows more information about the topic under discussion. For example:

The koala, which is native to Australia, mainly eats eucalyptus leaves.
Shakespeare, who was born in Stratford, moved to London.
Relative clauses, which have been the topic of this section, cause many problems for people trying (who are trying) to learn English.
Refuse collection, which takes place every Friday in this particular district, is paid for out of the local council tax.

In all four cases, the information inside the commas is only additional; the main clauses could stand on their own as perfectly grammatical, meaningful sentences in English.

Other relative pronouns

In addition to the relative pronouns which, who and that which we have already looked at, there are two others that we should mention: whose and where. First of all let's see a few examples of sentences containing whose.

Do you know the actor whose new show started on TV last night?
Those of you whose names are called out should go to the front row.
My mother, whose father was also a lawyer, married when she was 28.
I heard that a house whose owner had been out of the country for more than a year was demolished by mistake.
The treaty, whose signatories include all the major industrialised nations, was fully ratified last night.

It should be clear from these examples that whose is used to talk about possession in relative clauses. This possession is not restricted to just animate beings, but covers inanimate objects as well (the last two sentences). You can also see that whose is used in both defining and non-defining clauses - the third and sixth sentences are examples of non-defining clauses.
In relative clauses where is used place of in/at/on which, so:

This is the house where I was born.
This is the house in which I was born. (more formal)
The envelope where the number was written has been mislaid.
The envelope on which the number was written has been mislaid. (formal)
I'll never forget the concert where we first met each other.
I'll never forget the concert at which we first met. (formal)

When talking about places, it is quite easy to confuse this use of where with which, but you need to remember that where replaces a prepositional phrase usually containing in, at or on. Look at the next two sentences as an illustration of this:

London, which has been the capital of England for many centuries, is the largest city in the UK. (London as a thing.)
London, where I was born, is the largest city in the UK. (London as a place in which something happened.)

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