when adverb [OE. when, whan, whenne, whanne, AS. hwænne, 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.

☞ 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.

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.

-- Webster's unabridged 1913