shoulder vs body part

shoulder and body part both are nouns.

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

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

shoulder (noun)	body part (noun)
a narrow edge of land (usually unpaved) along the side of a road	any part of an organism such as an organ or extremity
the part of a garment that covers or fits over the shoulder
the part of the body between the neck and the upper arm
a ball-and-socket joint between the head of the humerus and a cavity of the scapula
a cut of meat including the upper joint of the foreleg

shoulder (verb)	body part (verb)
push with the shoulders
carry a burden, either real or metaphoric
lift onto one's shoulders