trigeminal vs nervus trigeminus

trigeminal and nervus trigeminus both are nouns.

Word	Noun	Adjective	Verb	Adverb
trigeminal	Yes	No	No	No
nervus trigeminus	Yes	No	No	No

As nouns, trigeminal and nervus trigeminus are synonyms defined as:

trigeminal and nervus trigeminus: the main sensory nerve of the face and motor nerve for the muscles of mastication

Other synonyms of trigeminal include fifth cranial nerve, trigeminal nerve, trigeminus.

trigeminal (noun)	nervus trigeminus (noun)
the main sensory nerve of the face and motor nerve for the muscles of mastication	the main sensory nerve of the face and motor nerve for the muscles of mastication