lightheartedness vs insouciance

lightheartedness and insouciance both are nouns.

Word	Noun	Adjective	Verb	Adverb
lightheartedness	Yes	No	No	No
insouciance	Yes	No	No	No

As nouns, lightheartedness and insouciance are synonyms defined as:

lightheartedness and insouciance: the cheerful feeling you have when nothing is troubling you

Other synonyms of lightheartedness include carefreeness, lightsomeness.

lightheartedness (noun)	insouciance (noun)
the cheerful feeling you have when nothing is troubling you	the cheerful feeling you have when nothing is troubling you