Quercus cerris vs oak tree

Quercus cerris and oak tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
Quercus cerris	Yes	No	No	No
oak tree	Yes	No	No	No

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

Quercus cerris: large deciduous tree of central and southern Europe and Asia Minor having lanceolate leaves with spiked lobes
oak tree: a deciduous tree of the genus Quercus; has acorns and lobed leaves

Other hypernyms of Quercus cerris include oak.

Quercus cerris (noun)	oak tree (noun)
large deciduous tree of central and southern Europe and Asia Minor having lanceolate leaves with spiked lobes	a deciduous tree of the genus Quercus; has acorns and lobed leaves