venous blood vessel vs vena

venous blood vessel and vena both are nouns.

Word	Noun	Adjective	Verb	Adverb
venous blood vessel	Yes	No	No	No
vena	Yes	No	No	No

As nouns, venous blood vessel and vena are synonyms defined as:

venous blood vessel and vena: a blood vessel that carries blood from the capillaries toward the heart

Other synonyms of venous blood vessel include vein.

venous blood vessel (noun)	vena (noun)
a blood vessel that carries blood from the capillaries toward the heart	a blood vessel that carries blood from the capillaries toward the heart