abdomen vs body part

abdomen and body part both are nouns.

Word	Noun	Adjective	Verb	Adverb
abdomen	Yes	No	No	No
body part	Yes	No	No	No

As nouns, body part is a hypernym of abdomen; that is, body part is a word with a broader meaning than abdomen:

abdomen: the region of the body of a vertebrate between the thorax and the pelvis
body part: any part of an organism such as an organ or extremity

abdomen (noun)	body part (noun)
the region of the body of a vertebrate between the thorax and the pelvis	any part of an organism such as an organ or extremity
the cavity containing the major viscera; in mammals it is separated from the thorax by the diaphragm