diploic vein vs vena

diploic vein and vena both are nouns.

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

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

diploic vein: one of the veins serving the spongy part of the cranial bones
vena: a blood vessel that carries blood from the capillaries toward the heart

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

diploic vein (noun)	vena (noun)
one of the veins serving the spongy part of the cranial bones	a blood vessel that carries blood from the capillaries toward the heart