trapezius muscle vs musculus trapezius

trapezius muscle and musculus trapezius both are nouns.

Word	Noun	Adjective	Verb	Adverb
trapezius muscle	Yes	No	No	No
musculus trapezius	Yes	No	No	No

As nouns, trapezius muscle and musculus trapezius are synonyms defined as:

trapezius muscle and musculus trapezius: either of two flat triangular muscles of the shoulder and upper back that are involved in moving the shoulders and arms

Other synonyms of trapezius muscle include cowl muscle, trapezius.

trapezius muscle (noun)	musculus trapezius (noun)
either of two flat triangular muscles of the shoulder and upper back that are involved in moving the shoulders and arms	either of two flat triangular muscles of the shoulder and upper back that are involved in moving the shoulders and arms