The Collaborative International Dictionary of English v.0.48:

Afterwards \Aft"er*wards\, Afterward \Aft"er*ward\, adv. [AS.
   [ae]fteweard, a., behind. See Aft, and -ward (suffix).
   The final s in afterwards is adverbial, orig. a genitive
   ending.]
   At a later or succeeding time.
   [1913 Webster]

WordNet (r) 3.0 (2006):

afterwards
    adv 1: happening at a time subsequent to a reference time; "he
           apologized subsequently"; "he's going to the store but
           he'll be back here later"; "it didn't happen until
           afterward"; "two hours after that" [syn: subsequently,
           later, afterwards, afterward, after, later on]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "afterwards":
   after, after a time, after a while, after all, after that,
   afterward, anon, before long, by and by, by destiny, ex post facto,
   fatally, hopefully, imminently, in aftertime, in the aftermath,
   in the future, in the sequel, later, next, predictably, probably,
   proximo, since, soon, subsequently, then, thereafter, thereon,
   thereupon, therewith, tomorrow