radicalism vs ideology

radicalism and ideology both are nouns.

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

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

radicalism: the political orientation of those who favor revolutionary change in government and society
ideology: an orientation that characterizes the thinking of a group or nation

Other hypernyms of radicalism include political orientation, political theory.

radicalism (noun)	ideology (noun)
the political orientation of those who favor revolutionary change in government and society	an orientation that characterizes the thinking of a group or nation
	imaginary or visionary theorization