gregariousness vs gregarious

gregariousness is a noun but gregarious is not a noun.

Word	Noun	Adjective	Verb	Adverb
gregariousness	Yes	No	No	No
gregarious	No	Yes	No	No

gregariousness (noun)	gregarious (noun)
the quality of being gregarious--having a dislike of being alone

gregariousness (adjective)	gregarious (adjective)
	(of animals) tending to form a group with others of the same species
	(of plants) growing in groups that are close together
	instinctively or temperamentally seeking and enjoying the company of others