eland vs common eland

eland and common eland both are nouns.

Word	Noun	Adjective	Verb	Adverb
eland	Yes	No	No	No
common eland	Yes	No	No	No

As nouns, common eland is a hyponym of eland; that is, common eland is a word with a more specific, narrower meaning than eland:

eland: either of two large African antelopes of the genus Taurotragus having short spirally twisted horns in both sexes
common eland: dark fawn-colored eland of southern and eastern Africa

Other hyponyms of eland include Taurotragus oryx, giant eland, Taurotragus derbianus.

eland (noun)	common eland (noun)
either of two large African antelopes of the genus Taurotragus having short spirally twisted horns in both sexes	dark fawn-colored eland of southern and eastern Africa