disease vs unwellness

disease and unwellness both are nouns.

Word	Noun	Adjective	Verb	Adverb
disease	Yes	No	No	No
unwellness	Yes	No	No	No

As nouns, unwellness is a hypernym of disease; that is, unwellness is a word with a broader meaning than disease:

disease: an impairment of health or a condition of abnormal functioning
unwellness: impairment of normal physiological function affecting part or all of an organism

Other hypernyms of disease include illness, malady, sickness.

disease (noun)	unwellness (noun)
an impairment of health or a condition of abnormal functioning	impairment of normal physiological function affecting part or all of an organism