Quercus variabilis vs oak

Quercus variabilis and oak both are nouns.

Word	Noun	Adjective	Verb	Adverb
Quercus variabilis	Yes	No	No	No
oak	Yes	No	No	No

As nouns, oak is a hypernym of Quercus variabilis; that is, oak is a word with a broader meaning than Quercus variabilis:

Quercus variabilis: medium to large deciduous tree of China, Japan, and Korea having thick corky bark
oak: a deciduous tree of the genus Quercus; has acorns and lobed leaves

Other hypernyms of Quercus variabilis include oak tree.

Quercus variabilis (noun)	oak (noun)
medium to large deciduous tree of China, Japan, and Korea having thick corky bark	a deciduous tree of the genus Quercus; has acorns and lobed leaves
	the hard durable wood of any oak; used especially for furniture and flooring