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Meaning of when

when

Pronunciation: (hwen, wen unstressed hw&schwan, w&schwan), [key]
—conj.
  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?
—pron.
  1. what time: Till when is the store open?
  2. which time: They left on Monday, since when we have heard nothing.
—n.
  1. the time of anything: the when and the where of an act.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.