when

Adverb

when (not comparable)

1. (interrogative) 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?
   1. (Internet, humorous, interrogative, often) 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?
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. (relative) 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.
4. (fused relative) 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. (informal) A circumstance or situation in which.
   • Love is when you can't get enough of someone.

Conjunction

when

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.

   Synonyms:

   as soon as, immediately, once, whenever

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.

   Synonyms:

   while

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.
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.

   Synonyms:

   given that

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.

   Synonyms:

   but, where, whereas

Pronoun

when

1. (interrogative) 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, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published...

Noun

when (plural whens)

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.2008, Paolo Aite, Lanscapes of the Psyche, Ipoc Press, →ISBN, page 151

Interjection

1. (humorous, often) 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 Drebin (Leslie Nielsen)
   • 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 American Cuisine, page 83
2. (obsolete) 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, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward]...
   • 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, of the Life of Sir John Old-castle, the Good Lord Cobham. […], London: […]...