Pronunciation: (hwen, wen; unstressed hwun, wun), [key]
1. at what time or period? how long ago? how soon?: When are they to arrive? When did the Roman Empire exist?
2. under what circumstances? upon what occasion?: When is a letter of condolence in order? When did you ever see such a crowd?
1. at what time: to know when to be silent.
2. at the time or in the event that: when we were young; when the noise stops.
3. at any time; whenever: He is impatient when he is kept waiting.
4. upon or after which; and then: We had just fallen asleep when the bell rang.
5. while on the contrary; considering that; whereas: Why are you here when you should be in school?
1. what time: Till when is the store open?
2. which time: They left on Monday, since when we have heard nothing.
the time of anything: the when and the where of an act.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.