We use which in questions as a determiner and interrogative pronoun to ask for specific information:

‘Which car are we going in?’ he asked Alexander.

Which museums did you visit?

Which do you prefer? Lemon cake or carrot cake?

We use which in indirect questions and statements:

In the Young Cook of Britain competition, the finalists were asked which famous person they would like to cook for.

Find out which way they’re going and we’ll follow.

We use which in relative clauses to refer to animals and to things:

We have seen a lot of changes which are good for business.

The cruise ship, which will depart from Liverpool for a fifteen-night Mediterranean cruise, returns to the Mersey on 29 September.

We also use which to introduce a relative clause when it refers to a whole clause or sentence:

She seemed more talkative than usual, which was because she was nervous.

People think I sit around drinking coffee all day. Which, of course, I do.

We often use which with prepositions. Some formal styles prefer to use a preposition before which rather than to leave the preposition ‘hanging’ at the end of the sentence:

There are several small ponds in which a variety of fish live. (or There are several small ponds which a variety of fish live in.)

We use of with which before other determiners (the, those, your) and pronouns (yours, them):

Which of the following features do you feel are important when choosing a house?

Which of your sisters lives in Boston?

There are a lot of high-street retailers. Which of them are offering the best value for money?