ague vs sickness

ague and sickness both are nouns.

Word	Noun	Adjective	Verb	Adverb
ague	Yes	No	No	No
sickness	Yes	No	No	No

As nouns, sickness is a hypernym of ague; that is, sickness is a word with a broader meaning than ague:

ague: a fit of shivering or shaking
sickness: impairment of normal physiological function affecting part or all of an organism

Other hypernyms of ague include illness, malady, unwellness.

ague (noun)	sickness (noun)
a mark placed above a vowel to indicate pronunciation	impairment of normal physiological function affecting part or all of an organism
a fit of shivering or shaking	the state that precedes vomiting
successive stages of chills and fever that is a symptom of malaria	defectiveness or unsoundness