idiosyncrasy vs specialness

idiosyncrasy and specialness both are nouns.

Word	Noun	Adjective	Verb	Adverb
idiosyncrasy	Yes	No	No	No
specialness	Yes	No	No	No

As nouns, specialness is a hypernym of idiosyncrasy; that is, specialness is a word with a broader meaning than idiosyncrasy:

idiosyncrasy: a behavioral attribute that is distinctive and peculiar to an individual
specialness: a distinguishing trait

Other hypernyms of idiosyncrasy include distinctiveness, peculiarity, speciality, specialty.

idiosyncrasy (noun)	specialness (noun)
a behavioral attribute that is distinctive and peculiar to an individual	a distinguishing trait
	the quality of being particular and pertaining to a specific case or instance