unbelief vs scepticism

unbelief and scepticism both are nouns.

Word	Noun	Adjective	Verb	Adverb
unbelief	Yes	No	No	No
scepticism	Yes	No	No	No

As nouns, scepticism is a hyponym of unbelief; that is, scepticism is a word with a more specific, narrower meaning than unbelief:

Other hyponyms of unbelief include agnosticism, skepticism, atheism.

unbelief (noun)	scepticism (noun)
a rejection of belief	the disbelief in any claims of ultimate knowledge
	doubt about the truth of something