hart vs wapiti

hart and wapiti both are nouns.

Word	Noun	Adjective	Verb	Adverb
hart	Yes	No	No	No
wapiti	Yes	No	No	No

As nouns, wapiti is a hypernym of hart; that is, wapiti is a word with a broader meaning than hart:

Other hypernyms of hart include American elk, Cervus elaphus, elk, red deer.

hart (noun)	wapiti (noun)
a male deer, especially an adult male red deer	large North American deer with large much-branched antlers in the male
	common deer of temperate Europe and Asia