crotch vs fanny

crotch and fanny both are nouns.

Word	Noun	Adjective	Verb	Adverb
crotch	Yes	No	No	No
fanny	Yes	No	No	No

As nouns, fanny is a hyponym of crotch; that is, fanny is a word with a more specific, narrower meaning than crotch:

crotch (noun)	fanny (noun)
the angle formed by the inner sides of the legs where they join the human trunk	the fleshy part of the human body that you sit on
external sex organ	external female sex organs
the region of the angle formed by the junction of two branches