Definition of which in English:


determiner & interrogative pronoun

  • Asking for information specifying one or more people or things from a definite set.

    [as pronoun] ‘which are the best varieties of grapes for long keeping?’
    ‘which of the suspects murdered him?’
    [as determiner] ‘which way is the wind blowing?’
    which, a fact which, something which
    View synonyms

determiner & relative pronoun

  • Used referring to something previously mentioned when introducing a clause giving further information.

    [as pronoun] ‘a conference in Vienna which ended on Friday’
    [after preposition] ‘it was a crisis for which he was totally unprepared’
    [as determiner, after preposition] ‘your claim ought to succeed, in which case the damages will be substantial’


On the differences between which and that in relative clauses, see that


  • which is which

    • Used to convey that it is difficult to distinguish between two or more people or things.

      ‘there is no confusion as to which is which’
      • ‘I can, like the animals on the farm, no longer tell which is which.’
      • ‘I'm just having trouble figuring out which is which!’
      • ‘The interrogator talks to both via a teletype machine, and his goal is to figure out which is which.’
      • ‘And that can make it hard to distinguish which is which.’
      • ‘I keep getting them mixed up, and I have to concentrate to remember which is which, and it's annoying.’
      • ‘The writers suggest ways to distinguish which is which in any given congregation.’
      • ‘I'll let you figure out which is which, it's not much of a puzzler.’
      • ‘I can't recall offhand which is which (though you could figure it out.’
      • ‘By the time you're done mixing it all together, it's hard to tell which is which.’
      • ‘One is for a gift and one is for a service, but I can never remember which is which.’


Old English hwilc, from the Germanic bases of who and alike.