What does "when" mean?

Additional senses

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.
2. 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.
3. 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.