millenarianism vs millenniumism

millenarianism and millenniumism both are nouns.

Word	Noun	Adjective	Verb	Adverb
millenarianism	Yes	No	No	No
millenniumism	Yes	No	No	No

As nouns, millenarianism and millenniumism are synonyms defined as:

millenarianism and millenniumism: belief in the Christian doctrine of the millennium mentioned in the Book of Revelations

Other synonyms of millenarianism include chiliasm, millenarism.

millenarianism (noun)	millenniumism (noun)
belief in the Christian doctrine of the millennium mentioned in the Book of Revelations	belief in the Christian doctrine of the millennium mentioned in the Book of Revelations