lumbar plexus vs plexus

lumbar plexus and plexus both are nouns.

Word	Noun	Adjective	Verb	Adverb
lumbar plexus	Yes	No	No	No
plexus	Yes	No	No	No

As nouns, plexus is a hypernym of lumbar plexus; that is, plexus is a word with a broader meaning than lumbar plexus:

lumbar plexus: a lymphatic plexus located along the lower portion of the aorta and iliac vessels
plexus: a network of intersecting blood vessels or intersecting nerves or intersecting lymph vessels

Other hypernyms of lumbar plexus include rete.

lumbar plexus (noun)	plexus (noun)
a plexus of nerves formed by the ventral branches of the first four lumbar nerves	a network of intersecting blood vessels or intersecting nerves or intersecting lymph vessels
a lymphatic plexus located along the lower portion of the aorta and iliac vessels