nausea vs symptom

nausea and symptom both are nouns.

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

As nouns, symptom is a hypernym of nausea; that is, symptom is a word with a broader meaning than nausea:

nausea: the state that precedes vomiting
symptom: (medicine) any sensation or change in bodily function that is experienced by a patient and is associated with a particular disease

nausea (noun)	symptom (noun)
disgust so strong it makes you feel sick	anything that accompanies X and is regarded as an indication of X's existence
the state that precedes vomiting	(medicine) any sensation or change in bodily function that is experienced by a patient and is associated with a particular disease