@Warsaw Will - Sorry for long delay replying!

Thanks for pointing out my mistake . Of course afterward is an adverb of time. A momentary mental glitch on my part, left unchecked in the haste of finishing and sending my post. I trust everything else was in order!

The adverbial suffix "-wards" in standard English is equivalent in intent to "-warts" in German, which is an inflection (specifically, gerund) of the verb "werden", to become; coupled with its initial preposition it implies the subject approaching a position from an assumed starting position, and by logical extension, the direction in which a subject is moving.

the adjectival "-ward" by contrast, describes the position or the point in time occupied by one grammatical person, relative to another (perhaps after having moved in the direction specified). Followed by "of", words ending in "-ward" become prepositional constructions (usages of the form "forwards of" are sub-standard), although only "forward of" (= in front of/ ahead of/ before) appears to have been in common use (to my knowledge..

"Afterwards" and "afterward" are used only adjectivally, and only to describe the point of time occupied by a person relative to another. According to the above scheme, "afterward" is legitimate while "afterwards" is presumably a corruption.