trapezius vs musculus trapezius

trapezius and musculus trapezius both are nouns.

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

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

trapezius 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 include cowl muscle, trapezius muscle.

trapezius (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