thoracic vs pectoral

thoracic is not a noun while pectoral is a noun.

Word	Noun	Adjective	Verb	Adverb
thoracic	No	Yes	No	No
pectoral	Yes	Yes	No	No

As adjectives, thoracic and pectoral are synonyms defined as:

thoracic (noun)	pectoral (noun)
	an adornment worn on the chest or breast
	either of two large muscles of the chest

thoracic (adjective)	pectoral (adjective)
of or relating to the chest or thorax	of or relating to the chest or thorax