significance vs unimportant

significance is a noun but unimportant is not a noun.

Word	Noun	Adjective	Verb	Adverb
significance	Yes	No	No	No
unimportant	No	Yes	No	No

significance (noun)	unimportant (noun)
the quality of being significant
a meaning that is not expressly stated but can be inferred
the message that is intended or expressed or signified

significance (adjective)	unimportant (adjective)
	not important
	devoid of importance, meaning, or force