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.]

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.

Source: Webster's Revised Unabridged Dictionary (1913)