idiosyncrasy vs distinctiveness

idiosyncrasy and distinctiveness both are nouns.

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

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

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

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

idiosyncrasy (noun)	distinctiveness (noun)
a behavioral attribute that is distinctive and peculiar to an individual	utter dissimilarity
	a distinguishing trait