red deer vs wapiti

red deer and wapiti both are nouns.

Word	Noun	Adjective	Verb	Adverb
red deer	Yes	No	No	No
wapiti	Yes	No	No	No

As nouns, red deer and wapiti are synonyms defined as:

Other synonyms of red deer include American elk, Cervus elaphus, elk.

red deer (noun)	wapiti (noun)
common deer of temperate Europe and Asia	large North American deer with large much-branched antlers in the male
	common deer of temperate Europe and Asia