pectoral muscle vs pectoralis

pectoral muscle and pectoralis both are nouns.

Word	Noun	Adjective	Verb	Adverb
pectoral muscle	Yes	No	No	No
pectoralis	Yes	No	No	No

As nouns, pectoral muscle and pectoralis are synonyms defined as:

pectoral muscle and pectoralis: either of two large muscles of the chest

Other synonyms of pectoral muscle include musculus pectoralis, pecs, pectoral.

pectoral muscle (noun)	pectoralis (noun)
either of two large muscles of the chest	either of two large muscles of the chest