The Oxford Dictionary (a British Dictionary) lists "afterward" as an American version of "afterwards": https://en.oxforddictionaries.com/definition/afterwards The Merriam-Webster Dictionary (an American dictionary) lists "afterwards" as a variant of "afterward", and searching for "afterwards" redirects you to "afterward": http://www.merriam-webster.com/dictionary/afterwards So it appears that "afterward" is American English and "afterwards" is British English. --------------------------------------------------------------------- I looked it up on Etymonline, and apparently the original word was "æftanweard", and the "s" was added "c. 1300, from afterward (q.v.)" as a "adverbial genitive -s". Apparently it was common in Old English for nouns functioning as adverbs to have an "s" added to the end: http://etymonline.com/index.php?term=afterward&allowed_in_frame=0 http://etymonline.com/index.php?term=afterwards&allowed_in_frame=0 https://en.wikipedia.org/wiki/Adverbial_genitive

Afterwards is correct.