nausea vs qualm

nausea and qualm both are nouns.

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

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

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

nausea (noun)	qualm (noun)
disgust so strong it makes you feel sick	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