iliolumbar vein vs vena

iliolumbar vein and vena both are nouns.

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

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

iliolumbar vein: a branch of the internal iliac vein
vena: a blood vessel that carries blood from the capillaries toward the heart

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

iliolumbar vein (noun)	vena (noun)
a branch of the internal iliac vein	a blood vessel that carries blood from the capillaries toward the heart