From Middle English which, hwic, wilche, hwilch, whilk, hwilc, from Old English hwelċ, from Proto-Germanic *hwilīkaz, derived from *hwaz, equivalent to who + like.

• enPR: wĭch, IPA: /wɪt͡ʃ/
• (non-wine-whine) enPR: hwĭch, IPA: /ʍɪt͡ʃ/

1. (interrogative) What, of those mentioned or implied.

   Which song shall we play?

   They couldn't decide which song to play.

   Which one is bigger?

   Show me which one is bigger.

2. The/Any ... that; whichever.

   Take which one you want.

   You may go which way you please.

3. (relative, formal outside certain phrases) Designates the one(s) previously mentioned.
   • 1860, Alfred Henry Forrester, Fairy footsteps, or, Lessons from legends, with illustr., by Alfred Crowquill, page 166 (Google Books view) ↗:

     After glaring upon the smoking philosopher, who took his misfortunes with such positive nonchalance, he growled out an oath in German, which language is particularly adapted for growling in; then, raising his hand, he dealt him a blow on his pipe, which sent it, like a rocket, into the midst of the players.

   He once owned a painting of the house, which painting would later be stolen.
   Yesterday, I met three men with long beards, which men I remember vividly.
   For several seconds he sat in silence, during which time the tea and sandwiches arrived.
   I'm thinking of getting a new car, in which case I'd get a red one.

• French: quel, quelle, quels, quelles
• German: welcher, welche, welches, welche
• Italian: quale
• Portuguese: qual
• Russian: кото́рый
• Spanish: cuál, cuáles

• French: lequel, laquelle, lesquels, lesquelles
• German: welcher, welche, welches, welche
• Italian: il quale, la quale, i quali, le quali, che
• Portuguese: qual, o qual, os quais, a qual, as quais
• Russian: кото́рый
• Spanish: cual, cuál, cuales, cuáles

1. (interrogative) What one or ones (of those mentioned or implied).

   Which is which?

   By now, you must surely know which is which.

   Which is bigger, the red one or the blue one?

   I'm unable to determine which is bigger.

   Which of these do you want to keep?

2. (not in common use) The/Any ones that; whichever.

   Please take which you please.

3. (relative) In a non-restrictive relative clause, referring to something previously mentioned.
   1. Referring to a preceding noun.

      Flour contains starch, which is a type of carbohydrate.

      I found my camera, which I thought I'd lost, under the bed.

      I entered the room, at the far end of which was a small table.

      • 1897 December (indicated as 1898), Winston Churchill, chapter II, in The Celebrity: An Episode, New York, N.Y.: The Macmillan Company; London: Macmillan & Co., Ltd., →OCLC ↗:

        Sunning himself on the board steps, I saw for the first time Mr. Farquhar Fenelon Cooke. […] A silver snaffle on a heavy leather watch guard which connected the pockets of his corduroy waistcoat, together with a huge gold stirrup in his Ascot tie, sufficiently proclaimed his tastes.

      • 1913, Mrs. [Marie] Belloc Lowndes, chapter II, in The Lodger, London: Methuen, →OCLC ↗; republished in Novels of Mystery: The Lodger; The Story of Ivy; What Really Happened, New York, N.Y.: Longmans, Green and Co., […], [1933], →OCLC ↗, page 0091 ↗:

        There was a neat hat-and-umbrella stand, and the stranger's weary feet fell soft on a good, serviceable dark-red drugget, which matched in colour the flock-paper on the walls.

      1. (mostly, archaic) Used of people (now generally who, whom, that; which remains possible with words also referred to by it such as baby, child).

         She had a young child, which cried incessantly.

   2. Referring to a preceding statement.

      The front door was open, which concerned me.

      He had to leave, which was very difficult.

      She saved my life, for which I am eternally grateful.

4. (relative, sometimes proscribed, see usage notes) In a restrictive relative clause, referring to a noun previously mentioned.

   This is the letter which I received.

   This is the letter in which he explains his decision.

   • 1611, The Holy Bible, […] (King James Version), London: […] Robert Barker, […], →OCLC ↗, Luke 1:1 ↗:

     Forasmuch as many have taken in hand to set forth in order a declaration of those things which are most surely believed among us...

   1. (mostly, archaic) Used of people.
      • 1526, [William Tyndale, transl.], The Newe Testamẽt […] (Tyndale Bible), [Worms, Germany: Peter Schöffer], →OCLC ↗, Acts:

        The men which acompanyed him on his waye stode amased, for they herde a voyce, butt sawe no man.

• every which way
• every which where
• which is which

• French: quel
• German: welcher, welche, welches, welche
• Italian: quale
• Portuguese: qual
• Russian: кото́рый
• Spanish: cuál

• French: qui (referring to the subject); que (referring to the object)
• German: der, welcher, was (referring back to a clause)
• Italian: che, cui
• Portuguese: que
• Russian: кото́рый
• Spanish: quien (if a person), que, el cual, la cual