illustriousness vs importance

illustriousness and importance both are nouns.

Word	Noun	Adjective	Verb	Adverb
illustriousness	Yes	No	No	No
importance	Yes	No	No	No

As nouns, importance is a hypernym of illustriousness; that is, importance is a word with a broader meaning than illustriousness:

illustriousness: the property possessed by something or someone of outstanding importance or eminence
importance: the quality of being important and worthy of note

illustriousness (noun)	importance (noun)
the property possessed by something or someone of outstanding importance or eminence	the quality of being important and worthy of note
	a prominent status