sickness vs qualm

sickness and qualm both are nouns.

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

As nouns, qualm is a hyponym of sickness; that is, qualm is a word with a more specific, narrower meaning than sickness:

Other hyponyms of sickness include kinetosis, motion sickness, morning sickness, queasiness, squeamishness.

sickness (noun)	qualm (noun)
impairment of normal physiological function affecting part or all of an organism	uneasiness about the fitness of an action (particularly for reasons of ethics, morals or propriety)
the state that precedes vomiting	a mild state of nausea
defectiveness or unsoundness