which which /wɪʧ/

pronoun

1. () Interrogative pronoun, used both substantively and adjectivally, and in direct and indirect questions, to ask for, or refer to, an individual person or thing among several of a class.  ( which )
   Interrogative pronoun, used both substantively and adjectivally, and in direct and indirect questions, to ask for, or refer to, an individual person or thing among several of a class.