Panthera leo vs lionet

Panthera leo and lionet both are nouns.

Word	Noun	Adjective	Verb	Adverb
Panthera leo	Yes	No	No	No
lionet	Yes	No	No	No

As nouns, lionet is a hyponym of Panthera leo; that is, lionet is a word with a more specific, narrower meaning than Panthera leo:

Panthera leo: large gregarious predatory feline of Africa and India having a tawny coat with a shaggy mane in the male
lionet: a small or young lion

Other hyponyms of Panthera leo include lion cub, lioness.

Panthera leo (noun)	lionet (noun)
large gregarious predatory feline of Africa and India having a tawny coat with a shaggy mane in the male	a small or young lion