That and which can be used interchangeably in most circumstances, Isabelle. That can even be used as an
alternative to who. Let's take a closer look.
who / which / that
Who, which and that are all relative pronouns and are used to introduce relative clauses. They can be used
as the subjects of verbs in relative clauses. As relative pronouns, who can only refer to people and
which can only refer to things. But that can refer to both people and things.
That when it refers to people denotes an informal style of English. Compare the following:
Note that who, which and that replace he, she, it and they and enable
us to join two clauses which would otherwise be separate.
Who is the woman wearing dark glasses who arrived five minutes ago?
'The Office' is a TV sit-com which / that is not suitable for young children.
Do you know anyone that could help me design web pages? - I know a German web artist who designed web pages for Lufthansa.
Who, which and that can also be used in a similar way as the objects of verbs in relative clauses in which
case they replace him, her, it and them. We can use whom instead of who as an object
relative pronoun in a more formal style of English. Compare the following:
Who is the woman wearing dark glasses? She arrived five minutes ago.
'The Office' is a British TV sit-com. It is not suitable for young children.
I know a German web artist. He designed web pages for Lufthansa.
Note that when who, which and that function as object relative pronouns, they are often left out of the
She's now living with the musician that / who she met at the pop concert.
She's now living with the musician whom she met at the pop concert.
She's now living with the musician. She met him at the pop concert.
Where are the Radiohead CDs which / that your brother borrowed last week?
Where are the Radiohead CDs? Your brother borrowed them last week.
that rather than which
She's now living with the musician she met at the pop concert.
Where are the Radiohead CDs your brother borrowed last week?
After quantifiers like everything, something, all and after the thing… we normally use that rather than which:
which but not that
Everything that is in this room once belonged to Elton John.
The thing that amazes me is how wide his interests were.
All that will be left after the auction are a few candlestick holders.
Where the relative pronoun refers to the whole of the previous clause, and not just to
the noun that precedes it, that cannot be used. In these instances, we have to use which:
Here which replaces this:
The explorer Sir Ranulph Fiennes ran in seven marathons in five different continents recently
which is amazing for a man of 59 who had a heart attack six months ago.
which but not that in non-identifying relative clauses
The explorer Sir Ranulph Fiennes ran in seven marathons in five different continents recently. This is amazing for
a man of 59 who had a double heart bypass operation six months ago.
In non-identifying relative clauses, which usually serve to provide additional, non-essential information and are separated by commas,
which is the relative pronoun that is normally used. That would be unusual.
Compare the following pairs of identifying and
non-identifying relative clauses:
Have you got any pieces for the guitar that are easy to play?
I lent him The Rain in Spain and Japanese Folk Song, which are easy to play.
The last symphony (that) he composed was the ninth symphony.
The ninth symphony, which was composed in the final year of his life, was not performed until after this death