From The Collaborative International Dictionary of English v.0.48 [gcide]:
When \When\, adv. [OE. when, whan, whenne, whanne, AS.
hw[ae]nne, hwanne, hwonne; akin to OS. hwan, OD. wan, OHG.
wanne, G. wann when, wenn if, when, Goth. hwan when, and to
E. who. ????. See Who.]
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1. At what time; -- used interrogatively.
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When shall these things be? --Matt. xxiv.
3.
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Note: See the Note under What, pron., 1.
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2. At what time; at, during, or after the time that; at or
just after, the moment that; -- used relatively.
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Kings may
Take their advantage when and how they list.
--Daniel.
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Book lore ne'er served, when trial came,
Nor gifts, when faith was dead. --J. H.
Newman.
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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.
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4. Which time; then; -- used elliptically as a noun.
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I was adopted heir by his consent;
Since when, his oath is broke. --Shak.
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Note: When was formerly used as an exclamation of surprise or
impatience, like what!
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Come hither; mend my ruff:
Here, when! thou art such a tedious lady! --J.
Webster.
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When as, When that, at the time that; when. [Obs.]
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When as sacred light began to dawn. --Milton.
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When that mine eye is famished for a look. --Shak.
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