Greenland caribou vs deer

Greenland caribou and deer both are nouns.

Word	Noun	Adjective	Verb	Adverb
Greenland caribou	Yes	No	No	No
deer	Yes	No	No	No

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

Greenland caribou: Arctic deer with large antlers in both sexes; called `reindeer' in Eurasia and `caribou' in North America
deer: distinguished from Bovidae by the male's having solid deciduous antlers

Other hypernyms of Greenland caribou include cervid.

Greenland caribou (noun)	deer (noun)
Arctic deer with large antlers in both sexes; called `reindeer' in Eurasia and `caribou' in North America	distinguished from Bovidae by the male's having solid deciduous antlers