We use 'who' to talk about people.

"The people who live in London."

We use that and which to talk about things.

"Did you drink the milk that was in the fridge?"

"I cleaned up the mess which you left in the kitchen."

Who, that and which are all used to introduce relative clauses into sentences.

What is a relative clause and why do I need one?

A clause is a part of a sentence which gives us more information about the subject.

Why do we use a relative clause?

For example, "The people who live in London are always very busy."

The extra information given by using 'who' tells us which people are always very busy, otherwise the sentence would read "The people are always very busy." We want to know which people.

"Did you drink the milk that was in the fridge?" would become

"Did you drink the milk?"

By introducing the relative clause 'that was in the fridge' we can provide more information about the milk.

"I cleaned up the mess which you left in the kitchen." would become

"I cleaned up the mess."

Using the relative clause 'which you left in the kitchen' tells us where the mess was.

What happens if we don't use a relative clause?

Relative clauses help us to construct more complex sentences. Without using who, that or which we would need to write two separate sentences:

"The people in London. They are always very busy."

"Did you drink the milk? It was in the fridge."

"You left a mess in the kitchen. I cleaned it up."

Why do I need to use complex sentences?

Showing you can use complex sentences will boost your grade in any English exam, HAVO, VWO, TEFL all reward the use of more complex language.

Give it a try for yourself!

Which of these sentences is correct:

"Can you see the man over there which is wearing a yellow shirt?"

"Did you go to the bakery who is on the corner of the high street?"

"Did you get your shoes from the new shop which has opened in the shopping mall?"

"The staff who work in the restaurant on the square are always very friendly."

The car who was being followed by the police was driving very fast.