unconcern vs nonchalance

unconcern and nonchalance both are nouns.

Word	Noun	Adjective	Verb	Adverb
unconcern	Yes	No	No	No
nonchalance	Yes	No	No	No

As nouns, unconcern and nonchalance are synonyms defined as:

unconcern and nonchalance: the trait of remaining calm and seeming not to care; a casual lack of concern

Other synonyms of unconcern include indifference.

unconcern (noun)	nonchalance (noun)
the trait of remaining calm and seeming not to care; a casual lack of concern	the trait of remaining calm and seeming not to care; a casual lack of concern
a feeling of lack of concern