solitary vs solitariness

solitary and solitariness both are nouns.

Word	Noun	Adjective	Verb	Adverb
solitary	Yes	Yes	No	No
solitariness	Yes	No	No	No

solitary (noun)	solitariness (noun)
one who lives in solitude	a disposition toward being alone
confinement of a prisoner in isolation from other prisoners	the state of being alone in solitary isolation

solitary (adjective)	solitariness (adjective)
being the only one; single and isolated from others
lacking companions or companionship
of plants and animals; not growing or living in groups or colonies
devoid of creatures
characterized by or preferring solitude