backward vs rearward

backward is not a noun while rearward is a noun.

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

As adverbs, backward and rearward are synonyms defined as:

Other synonyms of backward include back, backwards, rearwards.

backward (noun)	rearward (noun)
	direction toward the rear

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

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