used to ask for identification of one or ones out of a known or limited group

Which tie should I wear?

whichever

It will not fit, turn it which way you like

used to introduce a non-restrictive relative clause by modifying a noun referring to a preceding word, phrase, or clause

He may come, in which case I'll ask him

which thing, person, etc

Which is the cheapest?

whichever

Take which you like

used to introduce a non-restrictive clause:, esp in reference to an animal, thing, or idea

used in place of that to introduce a restrictive clause