article of faith vs belief

article of faith and belief both are nouns.

Word	Noun	Adjective	Verb	Adverb
article of faith	Yes	No	No	No
belief	Yes	No	No	No

As nouns, belief is a hypernym of article of faith; that is, belief is a word with a broader meaning than article of faith:

article of faith: an unshakable belief in something without need for proof or evidence
belief: any cognitive content held as true

article of faith (noun)	belief (noun)
an unshakable belief in something without need for proof or evidence	any cognitive content held as true
(Christianity) any of the sections into which a creed or other statement of doctrine is divided	a vague idea in which some confidence is placed