republicanism vs ideology

republicanism and ideology both are nouns.

Word	Noun	Adjective	Verb	Adverb
republicanism	Yes	No	No	No
ideology	Yes	No	No	No

As nouns, ideology is a hypernym of republicanism; that is, ideology is a word with a broader meaning than republicanism:

republicanism: the political orientation of those who hold that a republic is the best form of government
ideology: an orientation that characterizes the thinking of a group or nation

Other hypernyms of republicanism include political orientation, political theory.

republicanism (noun)	ideology (noun)
the political orientation of those who hold that a republic is the best form of government	an orientation that characterizes the thinking of a group or nation
	imaginary or visionary theorization