spontaneity vs spontaneous

spontaneity is a noun but spontaneous is not a noun.

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

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

spontaneity (adjective)	spontaneous (adjective)
	happening or arising without apparent external cause
	said or done without having been planned or written in advance