Mithraism vs religious belief

Mithraism and religious belief both are nouns.

Word	Noun	Adjective	Verb	Adverb
Mithraism	Yes	No	No	No
religious belief	Yes	No	No	No

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

Mithraism: ancient Persian religion; popular among Romans during first three centuries a.d.
religious belief: a strong belief in a supernatural power or powers that control human destiny

Other hypernyms of Mithraism include faith, religion.

Mithraism (noun)	religious belief (noun)
ancient Persian religion; popular among Romans during first three centuries a.d.	a strong belief in a supernatural power or powers that control human destiny