Mustela nivalis vs weasel

Mustela nivalis and weasel both are nouns.

Word	Noun	Adjective	Verb	Adverb
Mustela nivalis	Yes	No	No	No
weasel	Yes	No	No	No

As nouns, weasel is a hypernym of Mustela nivalis; that is, weasel is a word with a broader meaning than Mustela nivalis:

Mustela nivalis: of Europe
weasel: small carnivorous mammal with short legs and elongated body and neck

Mustela nivalis (noun)	weasel (noun)
of Europe	small carnivorous mammal with short legs and elongated body and neck
	a person who is regarded as treacherous or sneaky