retromandibular vein vs vena retromandibularis

retromandibular vein and vena retromandibularis both are nouns.

Word	Noun	Adjective	Verb	Adverb
retromandibular vein	Yes	No	No	No
vena retromandibularis	Yes	No	No	No

As nouns, retromandibular vein and vena retromandibularis are synonyms defined as:

retromandibular vein and vena retromandibularis: posterior branch of the facial vein; formed by temporal veins in front of the ear

Other synonyms of retromandibular vein include posterior facial vein.

retromandibular vein (noun)	vena retromandibularis (noun)
posterior branch of the facial vein; formed by temporal veins in front of the ear	posterior branch of the facial vein; formed by temporal veins in front of the ear