panther vs Felis onca

panther and Felis onca both are nouns.

Word	Noun	Adjective	Verb	Adverb
panther	Yes	No	No	No
Felis onca	Yes	No	No	No

As nouns, panther and Felis onca are synonyms defined as:

panther and Felis onca: a large spotted feline of tropical America similar to the leopard; in some classifications considered a member of the genus Felis

Other synonyms of panther include jaguar, Panthera onca.

panther (noun)	Felis onca (noun)
a leopard in the black color phase	a large spotted feline of tropical America similar to the leopard; in some classifications considered a member of the genus Felis
a large spotted feline of tropical America similar to the leopard; in some classifications considered a member of the genus Felis
large American feline resembling a lion