Hippopotamus amphibius vs river horse

Hippopotamus amphibius and river horse both are nouns.

Word	Noun	Adjective	Verb	Adverb
Hippopotamus amphibius	Yes	No	No	No
river horse	Yes	No	No	No

As nouns, Hippopotamus amphibius and river horse are synonyms defined as:

Hippopotamus amphibius and river horse: massive thick-skinned herbivorous animal living in or around rivers of tropical Africa

Other synonyms of Hippopotamus amphibius include hippo, hippopotamus.

Hippopotamus amphibius (noun)	river horse (noun)
massive thick-skinned herbivorous animal living in or around rivers of tropical Africa	massive thick-skinned herbivorous animal living in or around rivers of tropical Africa