Synonyms for When:

adj.

following (adjective)
ensuing.

adv.

then (adverb)
then.

conj.

though (conjunction)
at, while, During, meanwhile, at the same time.

n.

at the same time, concurrent, all the time, If, together, even as, simultaneous. before, all, sometime, Until, This, here, then, last, Whenever. how, just, where has someone/something gotten to?, do with, what (has) happened to something, anyway, kindly, what has/will become of, what's gotten into someone?, keep. when (noun)
once.

Other synonyms:

concurrent, Whenever, simultaneous, then. sometime, Until, together, This. last, here. before, all. as
During.
mean time
meanwhile.

Usage examples for when

  1. When they do, I know that I didn't have them. – Indian Summer by William D. Howells
  2. But when the heart is hongry, then- ah, yes, that is ozer thing. – Marie by Laura E. Richards
  3. But when it does? – The Reckoning by Robert W. Chambers