thoracic vein vs vena

thoracic vein and vena both are nouns.

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

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

thoracic vein: veins that drain the thoracic walls
vena: a blood vessel that carries blood from the capillaries toward the heart

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

thoracic vein (noun)	vena (noun)
veins that drain the thoracic walls	a blood vessel that carries blood from the capillaries toward the heart