From Middle English when(ne), whan(ne), from Old English hwenne, hwænne, hwonne (“when”), from Proto-Germanic *hwannē (“at what time, when”), from Proto-Indo-European *kʷo-, *kʷi- (“interrogative base”). Cognate with Dutch wanneer (“when”) and wen (“when, if”), German wann (“when”) and wenn (“when, if”), Gothic 𐍈𐌰𐌽 (ƕan, “when, how”), Latin quandō (“when”). More at who.
Interjection sense: a playful misunderstanding of "say when" (i.e. say when you want me to stop) as "say [the word] when".
when (not comparable)
- (interrogative) Used to introduce questions about time.
- When will they arrive?
- Used to introduce indirect questions about time.
- Do you know when they arrived?
- Do you know when they will arrive?
- Do you know when they arrive?
Usage notes 
- Used interrogatively, in either a direct or indirect question
- Afrikaans: wanneer (af)
- Albanian: kur (sq)
- American Sign Language: 1@NearTipFinger-PalmDown-1@CenterChesthigh-FingerUp CirclesHoriz 1@TipFinger-PalmDown-1@CenterChesthigh-FingerUp
- Arabic: مَتى (ar) (mátā)
- Egyptian: امتى (imta)
- Armenian: երբ (hy) (yerb)
- Aromanian: cãndu (rup)
- Azeri: haçan (az)
- Basque: noiz (eu)
- Belarusian: калі (be) (kalí)
- Bulgarian: кога (bg) (kogá)
- Burmese: (in the future) ဘယ်တော့ (my) (bèdaw.), (in the past) ဘယ်တုန်းက (my) (bèdoun:ga.)
- Catalan: quan (ca)
- Central Atlas Tamazight: ⵎⴰⵏ ⴰⴽⵓⴷ (man akud), ⵎⴰⵏⴰⴳⵓ (managu), ⵎⴰⵏⵜⵓⵔ (mantur), ⵎⵍⵎⵉ (mlmi)
- Chamicuro: na'kolyaye
- Mandarin: 甚麼時候 (cmn), 什么时候 (cmn) (shénme shíhòu), (literary) 何時 (cmn), 何时 (cmn) (héshí)
- Czech: kdy (cs)
- Dalmatian: cand
- Danish: hvornår (da)
- Dutch: wanneer (nl)
- Esperanto: kiam (eo)
- Estonian: millal (et), kunas (et)
- Faroese: nær (fo)
- Finnish: milloin (fi), koska (fi)
- French: quand (fr)
- Old French: quant
- Georgian: როდის (ka) (rodis)
- German: wann (de)
- Old High German: wanne
- Greek: πότε (el) (póte)
- Greenlandic: (past) qanga (kl), (future) qaqugu (kl)
- Guernésiais: quaend
- Hebrew: please add this translation if you can
- Hindi: कब (hi) (kab)
- Hungarian: mikor (hu)
- Icelandic: hvenær (is)
- Indonesian: kapan (id)
- Irish: cathain (ga), cá huair (ga), cén uair (ga)
- Old Irish: cuin
- Italian: quando (it)
- Japanese: 何時 (ja) (いつ, itsu), いつ (ja) (itsu)
- Kazakh: қашан (kk) (qaşan)
- Khmer: អង្កាល់ណា (km) (ɑngkaal naa), នៅពេលណា (km) (nɨv peel naa)
- Korean: 언제 (ko) (eonje)
- Krio: ustem
- Kurmanji: kengî (ku)
- Sorani: کهی (ku)
- At what time.
- They were told when to sleep.
- At such time as.
- I’m happiest when I’m working.
- As soon as.
- I’ll do it when I get the time.
- At a time in the past,
- It was raining when I came yesterday.
- 2012 April 22, Sam Sheringham, “Liverpool 0-1 West Brom”, BBC Sport:
- The Baggies had offered little threat until the 28th minute, but when their first chance came it was a clear one.
Derived terms 
at what time
- Latin: quandō (la), quandō (la)
- Latvian: kad (lv)
- Macedonian: кога (mk) (kóga)
- Malay: masa (ms)
- Maori: iwhea nonawhea āwhea (mi)
- Norwegian: når (no)
- Persian: وقتی (fa) (vaqti), وقتی که (fa) (vaqti ke), زمانی که (fa) (zamâni ke), در زمان (fa) (dar zamân-e), به هنگام (fa) (be hangâm-e), هنگامی که (fa) (hangâmi ke), چون (fa) (čon)
- Polish: kiedy (pl)
- Portuguese: quando (pt)
- Romanian: când (ro)
- Russian: когда (ru) (kogdá) , в то время как (ru) (v to vrémja kak)
- Scots: whan
- Scottish Gaelic: cuin (gd)
- Cyrillic: када (sh)
- Roman:kada (sh)
- Slovak: kedy (sk)
- Slovene: ko (sl)
- Spanish: cuando (es)
- Swedish: när (sv)
- Thai: เมื่อใด (th) (mêua dai)
- Ukrainian: коли (uk) (kolý)
- Urdu: جب (ur) (jab)
- Vietnamese: khi nào (vi), khi (vi), lúc nào (vi)
- Welsh: pryd (cy)
- Yiddish: ווען (yi) (ven)
- The translations below need to be checked and inserted above into the appropriate translation tables, removing any numbers. Numbers do not necessarily match those in definitions. See instructions at Help:How to check translations.
Translations to be checked
- Malagasy: rehefa (future)
- Maltese: please add this translation if you can
- Maori: please add this translation if you can
- Nepali: please add this translation if you can
- Old English: þā (1,2,3)
- Oriya: please add this translation if you can
- Romanian: când (1,2,3), atunci când (2,3)
- Tamil: please add this translation if you can
- Thai: เมื่อ (mêua)
- Vietnamese: please add this translation if you can
- Welsh: pan (cy)
- (interrogative) What time; which time
- Since when do I need your permission?
when (plural whens)
- The time.
- A good article will cover the who, the what, the when, the where, the why and the how.
See also 
- That's enough, a command to stop adding something, especially an ingredient of food or drink.
- 2004, Andy Husbands and Joe Yonan, The Fearless Chef: Innovative Recipes from the Edge of American Cuisine, page 83:
- When we go out to a restuarant, we're the guys who never say "when" when the waiter is grinding fresh pepper on our salads.
- 2009, Margaret Atwood, The Blind Assassin, page 111:
- He keeps the bottle in the top bureau drawer; he takes it out, and two glasses, and pours. Say when.
- 2011, Fritz Allhoff and Dave Monroe, Porn - Philosophy for Everyone: How to Think With Kink:
- Producers have the power to say "when" when the actress involved is too stressed to continue. That's responsible filmmaking.