pericardial space vs cavum

pericardial space and cavum both are nouns.

Word	Noun	Adjective	Verb	Adverb
pericardial space	Yes	No	No	No
cavum	Yes	No	No	No

As nouns, cavum is a hypernym of pericardial space; that is, cavum is a word with a broader meaning than pericardial space:

pericardial space: the space between the layers of the pericardium that contains fluid that lubricates the membrane surfaces and allows easy heart movement
cavum: (anatomy) a natural hollow or sinus within the body

Other hypernyms of pericardial space include bodily cavity, cavity.

pericardial space (noun)	cavum (noun)
the space between the layers of the pericardium that contains fluid that lubricates the membrane surfaces and allows easy heart movement	(anatomy) a natural hollow or sinus within the body