pectoralis vs pecs

pectoralis and pecs both are nouns.

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

As nouns, pectoralis and pecs are synonyms defined as:

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

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