circumflex vein vs vena

circumflex vein and vena both are nouns.

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

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

circumflex vein: any of several curved parallel veins accompanying arteries of the same name
vena: a blood vessel that carries blood from the capillaries toward the heart

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

circumflex vein (noun)	vena (noun)
any of several curved parallel veins accompanying arteries of the same name	a blood vessel that carries blood from the capillaries toward the heart