solitary vs lonesome

solitary is a noun but lonesome is not a noun.

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

As adjectives, solitary and lonesome are synonyms defined as:

solitary and lonesome: being the only one; single and isolated from others

Other synonyms of solitary include lone, only, sole.

solitary (noun)	lonesome (noun)
one who lives in solitude
confinement of a prisoner in isolation from other prisoners

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