paganism vs pagan religion

paganism and pagan religion both are nouns.

Word	Noun	Adjective	Verb	Adverb
paganism	Yes	No	No	No
pagan religion	Yes	No	No	No

As nouns, paganism and pagan religion are synonyms defined as:

paganism and pagan religion: any of various religions other than Christianity or Judaism or Islamism

Other synonyms of paganism include heathenism.

paganism (noun)	pagan religion (noun)
any of various religions other than Christianity or Judaism or Islamism	any of various religions other than Christianity or Judaism or Islamism