female chest vs pectus

female chest and pectus both are nouns.

Word	Noun	Adjective	Verb	Adverb
female chest	Yes	No	No	No
pectus	Yes	No	No	No

As nouns, pectus is a hypernym of female chest; that is, pectus is a word with a broader meaning than female chest:

female chest: the chest of a woman
pectus: the part of the human torso between the neck and the diaphragm or the corresponding part in other vertebrates

Other hypernyms of female chest include chest, thorax.

female chest (noun)	pectus (noun)
the chest of a woman	the part of the human torso between the neck and the diaphragm or the corresponding part in other vertebrates