pericardial vein vs vena

pericardial vein and vena both are nouns.

Word	Noun	Adjective	Verb	Adverb
pericardial vein	Yes	No	No	No
vena	Yes	No	No	No

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

pericardial vein: several small veins from the pericardium
vena: a blood vessel that carries blood from the capillaries toward the heart

Other hypernyms of pericardial vein include vein, venous blood vessel.

pericardial vein (noun)	vena (noun)
several small veins from the pericardium	a blood vessel that carries blood from the capillaries toward the heart