importance vs important

importance is a noun but important is not a noun.

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

importance (noun)	important (noun)
the quality of being important and worthy of note
a prominent status

importance (adjective)	important (adjective)
	of great significance or value
	of extreme importance; vital to the resolution of a crisis
	important in effect or meaning
	having or suggesting a consciousness of high position
	having authority or ascendancy or influence