felicitousness vs felicity

felicitousness and felicity both are nouns.

Word	Noun	Adjective	Verb	Adverb
felicitousness	Yes	No	No	No
felicity	Yes	No	No	No

As nouns, felicitousness and felicity are synonyms defined as:

felicitousness and felicity: pleasing and appropriate manner or style (especially manner or style of expression)

felicitousness (noun)	felicity (noun)
pleasing and appropriate manner or style (especially manner or style of expression)	pleasing and appropriate manner or style (especially manner or style of expression)
	state of well-being characterized by emotions ranging from contentment to intense joy