Greek Orthodox vs religion

Greek Orthodox is not a noun while religion is a noun.

Word	Noun	Adjective	Verb	Adverb
Greek Orthodox	No	Yes	No	No
religion	Yes	No	No	No

Greek Orthodox (noun)	religion (noun)
	a strong belief in a supernatural power or powers that control human destiny
	an institution to express belief in a divine power

Greek Orthodox (adjective)	religion (adjective)
of or relating to or characteristic of the Eastern Orthodox Church