common oak vs Quercus robur

common oak and Quercus robur both are nouns.

Word	Noun	Adjective	Verb	Adverb
common oak	Yes	No	No	No
Quercus robur	Yes	No	No	No

As nouns, common oak and Quercus robur are synonyms defined as:

common oak and Quercus robur: medium to large deciduous European oak having smooth leaves with rounded lobes; yields hard strong light-colored wood

Other synonyms of common oak include English oak, pedunculate oak.

common oak (noun)	Quercus robur (noun)
medium to large deciduous European oak having smooth leaves with rounded lobes; yields hard strong light-colored wood	medium to large deciduous European oak having smooth leaves with rounded lobes; yields hard strong light-colored wood