leftism vs ideology

leftism and ideology both are nouns.

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

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

leftism: the ideology of the political left; belief in or support of the tenets of the political left
ideology: an orientation that characterizes the thinking of a group or nation

Other hypernyms of leftism include political orientation, political theory.

leftism (noun)	ideology (noun)
the ideology of the political left; belief in or support of the tenets of the political left	an orientation that characterizes the thinking of a group or nation
	imaginary or visionary theorization