Afghan hound vs hound dog

Afghan hound and hound dog both are nouns.

Word	Noun	Adjective	Verb	Adverb
Afghan hound	Yes	No	No	No
hound dog	Yes	No	No	No

As nouns, hound dog is a hypernym of Afghan hound; that is, hound dog is a word with a broader meaning than Afghan hound:

Afghan hound: tall graceful breed of hound with a long silky coat; native to the Near East
hound dog: any of several breeds of dog used for hunting typically having large drooping ears

Other hypernyms of Afghan hound include hound.

Afghan hound (noun)	hound dog (noun)
tall graceful breed of hound with a long silky coat; native to the Near East	any of several breeds of dog used for hunting typically having large drooping ears