femoral vein vs vena

femoral vein and vena both are nouns.

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

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

femoral vein: a vein that accompanies the femoral artery in the same sheath; a continuation of the popliteal vein; becomes the external iliac vein
vena: a blood vessel that carries blood from the capillaries toward the heart

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

femoral vein (noun)	vena (noun)
a vein that accompanies the femoral artery in the same sheath; a continuation of the popliteal vein; becomes the external iliac vein	a blood vessel that carries blood from the capillaries toward the heart