thorax vs female chest

thorax and female chest both are nouns.

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

As nouns, female chest is a hyponym of thorax; that is, female chest is a word with a more specific, narrower meaning than thorax:

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

Other hyponyms of thorax include bust, male chest.

thorax (noun)	female chest (noun)
part of an insect's body that bears the wings and legs	the chest of a woman
the part of the human torso between the neck and the diaphragm or the corresponding part in other vertebrates
the middle region of the body of an arthropod between the head and the abdomen