withers vs body part

withers and body part both are nouns.

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

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

withers: the highest part of the back at the base of the neck of various animals especially draft animals
body part: any part of an organism such as an organ or extremity

withers (noun)	body part (noun)
the highest part of the back at the base of the neck of various animals especially draft animals	any part of an organism such as an organ or extremity