when /ˈhwɛn, ˈwɛn, (h)wən/
 (ad.)何時,什?時候(conj.)當…時;那時,然後;可是,而 什?時候
 When adv.
 1. At what time; -- used interrogatively.
    When shall these things be?   --Matt. xxiv. 3.
 Note: ☞ See the Note under What, pron., 1.
 2. At what time; at, during, or after the time that; at or just after, the moment that; -- used relatively.
 Kings may
 Take their advantage when and how they list.   --Daniel.
 Book lore ne'er served, when trial came,
 Nor gifts, when faith was dead.   --J. H. Newman.
 3. While; whereas; although; -- used in the manner of a conjunction to introduce a dependent adverbial sentence or clause, having a causal, conditional, or adversative relation to the principal proposition; as, he chose to turn highwayman when he might have continued an honest man; he removed the tree when it was the best in the grounds.
 4. Which time; then; -- used elliptically as a noun.
 I was adopted heir by his consent;
 Since when, his oath is broke.   --Shak.
 Note: ☞ When was formerly used as an exclamation of surprise or impatience, like what!
 Come hither; mend my ruff:
 Here, when! thou art such a tedious lady!   --J. Webster.
 When as, When that, at the time that; when. [Obs.]
    When as sacred light began to dawn.   --Milton.
    When that mine eye is famished for a look.   --Shak.
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 when
      adv : as soon as; "once we are home, we can rest" [syn: once]