Who, which and that can be the subjects of the verbs in relative clauses. Who refers to people and which to things; that can refer to both people and things.
- The boy who stole the watch was punished. (NOT The boy which stole …)
- It is a book which will interest children of all ages. (NOT It is a book who will …)
- The people that/who live next door keep having all-night parties.
- These are the keys that open the front and back door.
Who, whom, which and that can also be used as the objects of verbs in relative clauses. Who is informal as an object; in a more formal style whom is used.
- He is married to somebody who I really don’t like. (Informal)
- He is married to somebody whom I really don’t like. (Formal)
Relative pronouns as conjunctions
Relative pronouns serve two purposes: they act as subjects or objects inside their relative clauses, and at the same time they connect relative clauses to nouns or pronouns in other clauses – rather like conjunctions.
- I have found the car keys. You were looking for them.
- I have found the car keys which you were looking for.
- This is Mr Peter. You met him last year.
- This is Mr Peter whom you met last year.
- Here is an article. It might interest you.
- Here is an article which might interest you.
Correct use of the relative pronouns
Who, whom and whose
The pronouns who, whom and whose are generally only used for persons. Occasionally they are used for some animals and other inanimate objects too.
- A boy who does not play games will never be healthy.
- This is the woman whose husband was killed by the dacoits.
- I have an Alsatian whose name is Bruce.
- This is John Paul whom I used to know as a child.
- The ancients worshipped the moon whom they called Diana.
Which is used for animals and inanimate things.
- Mangoes which are over-ripe should be thrown away.
- The horse which won the race is called Handsome.
- This is a case which calls for careful investigation.
Which is also used to refer to a previous statement.
- The man said he was a police officer, which was not true.
- He wants me to give up his claim, which is impossible.
- He happened to be there at the time, which was fortunate.
That is used for persons and things.
- This is the boy that won the first prize.
- Here is the man that I told you of.
- This is the monument that was built by Shah Jehan.
- Uneasy lies the head that wears a crown.
Note that the relative pronoun that is used only in identifying relative clauses. In this respect it is different from who and which, as these can be used also in non-identifying relative clauses which merely give some information about the antecedent.
Another difference between that and who, which, is that while who and which can be used in the possessive case (whose, of which) and with prepositions (of whom, to whom, by which etc.) that cannot be used so.
- This is my boy of whom I am proud.
- This is the man whose house was burgled.
- I have an axe with which I cut wood.
You cannot substitute that for of whom, whose or with which in these sentences.
What is used only to refer to things and not persons. When used as a relative pronoun what means that which.
- I mean what (= that which) I say.
- What (= that which) is one man’s meat is another man’s poison.
- Take down what (= that which) I dictate.
- I saw what looked like a flying saucer.
- What cannot be cured must be endured.
As is used as a relative pronoun after such, and sometimes after the same.
- He is such a man as I honour.
- His reaction was such as might have been expected.
- My position is the same as yours.
After a negative, the word but is used as a relative pronoun in the sense of who…not or which…not.
- There was not a man among them but hoped (= who did not hope) to get out alive.
- There is no rose but has (= which does not have) some thorn.
- There is none here but will (= who will not) support you.