hematemesis vs regurgitation

hematemesis and regurgitation both are nouns.

Word	Noun	Adjective	Verb	Adverb
hematemesis	Yes	No	No	No
regurgitation	Yes	No	No	No

As nouns, regurgitation is a hypernym of hematemesis; that is, regurgitation is a word with a broader meaning than hematemesis:

hematemesis: vomiting blood
regurgitation: the reflex act of ejecting the contents of the stomach through the mouth

Other hypernyms of hematemesis include disgorgement, emesis, puking, vomit, vomiting.

hematemesis (noun)	regurgitation (noun)
vomiting blood	the reflex act of ejecting the contents of the stomach through the mouth
	recall after rote memorization
	backflow of blood through a defective heart valve