nonchalance vs unconcern

nonchalance and unconcern both are nouns.

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

As nouns, nonchalance and unconcern are synonyms defined as:

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

Other synonyms of nonchalance include indifference.

nonchalance (noun)	unconcern (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