haematemesis vs emesis

haematemesis and emesis both are nouns.

Word	Noun	Adjective	Verb	Adverb
haematemesis	Yes	No	No	No
emesis	Yes	No	No	No

As nouns, emesis is a hypernym of haematemesis; that is, emesis is a word with a broader meaning than haematemesis:

haematemesis: vomiting blood
emesis: the reflex act of ejecting the contents of the stomach through the mouth

Other hypernyms of haematemesis include disgorgement, puking, regurgitation, vomit, vomiting.

haematemesis (noun)	emesis (noun)
vomiting blood	the reflex act of ejecting the contents of the stomach through the mouth