back matter vs matter

back matter and matter both are nouns.

Word	Noun	Adjective	Verb	Adverb
back matter	Yes	No	No	No
matter	Yes	No	Yes	No

As nouns, matter is a hypernym of back matter; that is, matter is a word with a broader meaning than back matter:

back matter (noun)	matter (noun)
written matter following the main text of a book	that which has mass and occupies space
	(used with negation) having consequence
	some situation or event that is thought about
	a vaguely specified concern
	a problem
	written works (especially in books or magazines)

back matter (verb)	matter (verb)
	have weight; have import, carry weight