dugong vs sea cow

dugong and sea cow both are nouns.

Word	Noun	Adjective	Verb	Adverb
dugong	Yes	No	No	No
sea cow	Yes	No	No	No

As nouns, sea cow is a hypernym of dugong; that is, sea cow is a word with a broader meaning than dugong:

dugong: sirenian tusked mammal found from eastern Africa to Australia; the flat tail is bilobate
sea cow: any of two families of large herbivorous aquatic mammals with paddle-shaped tails and flipper-like forelimbs and no hind limbs

Other hypernyms of dugong include sirenian, sirenian mammal.

dugong (noun)	sea cow (noun)
sirenian tusked mammal found from eastern Africa to Australia; the flat tail is bilobate	any of two families of large herbivorous aquatic mammals with paddle-shaped tails and flipper-like forelimbs and no hind limbs