pecs vs musculus pectoralis

pecs and musculus pectoralis both are nouns.

Word	Noun	Adjective	Verb	Adverb
pecs	Yes	No	No	No
musculus pectoralis	Yes	No	No	No

As nouns, pecs and musculus pectoralis are synonyms defined as:

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

pecs (noun)	musculus pectoralis (noun)
either of two large muscles of the chest	either of two large muscles of the chest