when

Adverb

1. At what time? At which time? Upon which occasion or circumstance? Used to introduce direct or indirect questions about time.
   • When will they arrive?
   • Do you know when they arrived?
   • I don't know when they arrived.

   1. (interrogative, Internet slang, often humorous) Used after a noun or noun phrase in isolation to express impatience with an anticipated future event.

      • The site's all bugged. Fix when?
      • Tank class buff when?
      • My fridge even restocks itself these days. Glorious AI overlords when?
2. At an earlier time and under different, usually less favorable, circumstances.
   • He's mister high and mighty now, but I remember him when.
3. At which, on which, during which: often omitted or replaced with that.
   • That was the day when the Twin Towers fell.
   • Not a week goes by when I don't mourn that loss.
   • The Celebrity, by arts unknown, induced Mrs. Judge Short and two other ladies to call at Mohair on a certain afternoon when Mr. Cooke was trying a trotter on the track.[…]Their example was followed by others at a time...
4. The time at, on or during which.
   • I recall when they were called the Greys.
   • Next year is when we elect a new mayor.
5. A circumstance or situation in which.
   • Love is when you can't get enough of someone.

Conjunction

1. At (or as soon as) that time that; at the (or any and every) time that; if.
   • Pavlov's dogs salivate when [i.e. at any and every time that] they hear a bell.
   • When [i.e. at any and every time that] he speaks to her, he is always polite.
   • Put your pencil down when [i.e. as soon as, at the moment that] the timer goes off.
2. During the time that; at the time of the action of the following clause or participle phrase.
   • They dream when [i.e. during the time that] they sleep.
   • I'm happiest when [during the time that, or at any time that] I’m working.
   • It was raining when I came yesterday.
3. At what time; at which time.
   • I am here till Friday, when [i.e. at which time] I leave for Senegal.
   • I was just walking down the street, when [i.e. at which time] all of a sudden it started to rain.
   • I am at London only to provide for Monday, when I shall use that favour which my Lady Bedford hath afforded me, of giving her name to my daughter; which I mention to you, […] - 1839, John Donne, The Works of John Donne:...
4. Since; given the fact that; considering that.
   • I don't see the point of putting up Christmas decorations when I am the only person who is going to see them.
5. Whereas; although; at the same time as; in spite of the fact that.
   • You're picking at your scabs when you should be letting them heal.
   • He keeps changing things when the existing system works perfectly well.
   • Oh age! / Where only wealthy men are counted happy: / How ſhall I pleaſe thee? how deſerve thy ſmiles? / When I am only rich in miſery? - c. 1604–1626, doubtfully attributed to Francis Beaumont, John Fletcher, “The...

Interjection

1. That's enough: a command asking someone to stop adding something, especially an ingredient or portion of food or drink; used in, or as if in, literal response to 'Say when'.
   • HOCKEN: Say “when”, Frank. / DREBIN: Whe— - 1982, Nancy Steen and Neil Thompson, “Rendezvous at Big Gulch (Terror in the Neighborhood)”, in Police Squad!, episode 3, spoken by Ed Hocken (Alan North), spoken by Frank...
   • When we go out to a restaurant, we're the guys who never say "when" when the waiter is grinding fresh pepper on our salads. - 2004, Andy Husbands, Joe Yonan, The Fearless Chef: Innovative Recipes from the Edge of...
   • He keeps the bottle in the top bureau drawer; he takes it out, and two glasses, and pours. Say when. When, please. - 2009, Margaret Atwood, The Blind Assassin, page 111:
2. Expressing impatience.
   • Why when I ſay?[…]Off with my boots, you rogues: you villaines, when?[…]Out you rogue[…] - c. 1590–1592 (date written), William Shakespeare, “The Taming of the Shrew”, in Mr. William Shakespeares Comedies, Histories, &...
   • Set parſon, ſet, the dice die in my hand: / VVhen parſon, vvhen! vvhat can ye finde no more? - 1600, [Michael Drayton, Richard Hathwaye, Anthony Munday, Robert Wilson], The First Part of the True and Honorable Historie,...
   • VVhy vvhen? begin Sir: I muſt ſtay your leiſure. - c. 1615 (date written), Tho[mas] Middleton, “More Dissemblers besides Women. A Comedy”, in Two New Playes. […], London: […] Humphrey Moseley, […], published 1657,...

   Coordinate Terms: what

Noun

1. The time at which something happens.
   • A good article will cover the who, the what, the when, the where, the why and the how.
   • For the moment, suffice it to say that the stories told through the whens and hows of building a scene differentiate individual desires and needs more clearly than shared speech was up to then able to communicate. -...

Pronoun

1. What time; which time.
   • Since when do I need your permission?
   • [...] ſhortly [...] I'le reſolue you [...] / Theſe happend accidents: till when, be cheerefull [...] - 1610–1611 (date written), William Shakespeare, “The Tempest”, in Mr. William Shakespeares Comedies, Histories, &...
   • Homer, to whom the Muses did carouse A great deep cup with heav'nly nectar fill'd, The greatest, deepest cup in Jove's great house, (For Jove himself had so expressly will'd) He drank off all, nor let one drop be...

Wikipedia

when