rearwards vs backward

rearwards is not an adjective while backward is an adjective.

Word	Noun	Adjective	Verb	Adverb
rearwards	No	No	No	Yes
backward	No	Yes	No	Yes

As adverbs, rearwards and backward are synonyms defined as:

Other synonyms of rearwards include back, backwards, rearward.

rearwards (adjective)	backward (adjective)
	directed or facing toward the back or rear
	(used of temperament or behavior) marked by a retiring nature
	retarded in intellectual development
	having made less than normal progress

rearwards (adverb)	backward (adverb)
at or to or toward the back or rear	in a manner or order or direction the reverse of normal
	in or to or toward a past time
	at or to or toward the back or rear