strong belief vs belief

strong belief and belief both are nouns.

Word	Noun	Adjective	Verb	Adverb
strong belief	Yes	No	No	No
belief	Yes	No	No	No

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

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

strong belief (noun)	belief (noun)
an unshakable belief in something without need for proof or evidence	any cognitive content held as true
	a vague idea in which some confidence is placed