oesophageal veins vs vena

oesophageal veins and vena both are nouns.

Word	Noun	Adjective	Verb	Adverb
oesophageal veins	Yes	No	No	No
vena	Yes	No	No	No

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

oesophageal veins: small veins from the esophagus emptying into the brachiocephalic vein or the azygos veins
vena: a blood vessel that carries blood from the capillaries toward the heart

Other hypernyms of oesophageal veins include vein, venous blood vessel.

oesophageal veins (noun)	vena (noun)
small veins from the esophagus emptying into the brachiocephalic vein or the azygos veins	a blood vessel that carries blood from the capillaries toward the heart