whitetail vs deer

whitetail and deer both are nouns.

Word	Noun	Adjective	Verb	Adverb
whitetail	Yes	No	No	No
deer	Yes	No	No	No

As nouns, deer is a hypernym of whitetail; that is, deer is a word with a broader meaning than whitetail:

whitetail: common North American deer; tail has a white underside
deer: distinguished from Bovidae by the male's having solid deciduous antlers

Other hypernyms of whitetail include cervid.

whitetail (noun)	deer (noun)
common North American deer; tail has a white underside	distinguished from Bovidae by the male's having solid deciduous antlers