Which

• POS: Definite Article, Pronoun

CIDE DICTIONARY

Which, pron. [OE. which, whilk, AS. hwilc, hwylc, hwelc, from the root of hwā who + līc body; hence properly, of what sort or kind; akin to OS. hwilik which, OFries. hwelik, D. welk, G. welch, OHG. welīh, hwelīh, Icel. hvīlīkr, Dan. & Sw. hvilken, Goth. hwileiks, hwleiks; cf. L. qualis. . See Who, and Like, a., and cf. Such.].

•  Of what sort or kind; what; what a; who.  [1913 Webster]

  "And which they weren and of what degree."  [1913 Webster]
•  A interrogative pronoun, used both substantively and adjectively, and in direct and indirect questions, to ask for, or refer to, an individual person or thing among several of a class; as, which man is it? which woman was it? which is the house? he asked which route he should take; which is best, to live or to die? See the Note under What, pron., 1.  [1913 Webster]

  "Which of you convinceth me of sin?"  [1913 Webster]
•  A relative pronoun, used esp. in referring to an antecedent noun or clause, but sometimes with reference to what is specified or implied in a sentence, or to a following noun or clause (generally involving a reference, however, to something which has preceded). It is used in all numbers and genders, and was formerly used of persons.  [1913 Webster]

  "And when thou fail'st -- as God forbid the hour! --
  Must Edward fall, which peril heaven forfend!"  [1913 Webster]

  "God . . . rested on the seventh day from all his work which he had made."  [1913 Webster]

  "Our Father, which art in heaven."  [1913 Webster]

  "The temple of God is holy, which temple ye are."  [1913 Webster]
•  A compound relative or indefinite pronoun, standing for any one which, whichever, that which, those which, the . . . which, and the like; as, take which you will.  [1913 Webster]

  " The which was formerly often used for which. The expressions which that, which as, were also sometimes used by way of emphasis."  [1913 Webster]

  " Which, referring to a series of preceding sentences, or members of a sentence, may have all joined to it adjectively. “All which, as a method of a proclamation, is very convenient.” Carlyle."  [1913 Webster]

  "Do not they blaspheme that worthy name by the which ye are called?"  [1913 Webster]

OXFORD DICTIONARY

Which, adj. & pron.
--interrog.adj. asking for choice from a definite set of alternatives (which John do you mean?; say which book you prefer; which way shall we go?).
--rel.adj. being the one just referred to; and this or these (ten years, during which time they admitted nothing; a word of advice, which action is within your power, will set things straight).
--interrog.pron.
1 which person or persons (which of you is responsible?).
2 which thing or things (say which you prefer).
--rel.pron. (poss. of which, whose)
1 which thing or things, usu. introducing a clause not essential for identification (cf. THAT pron. 7) (the house, which is empty, has been damaged).
2 used in place of that after in or that (there is the house in which I was born; that which you have just seen).

Idiom

which is which a phrase used when two or more persons or things are difficult to distinguish from each other.

Etymology

OE hwilc f. Gmc