spontaneity vs spontaneousness

spontaneity and spontaneousness both are nouns.

Word	Noun	Adjective	Verb	Adverb
spontaneity	Yes	No	No	No
spontaneousness	Yes	No	No	No

As nouns, spontaneity and spontaneousness are synonyms defined as:

spontaneity and spontaneousness: the quality of being spontaneous and coming from natural feelings without constraint

spontaneity (noun)	spontaneousness (noun)
the quality of being spontaneous and coming from natural feelings without constraint	the quality of being spontaneous and coming from natural feelings without constraint