Quercus texana vs oak

Quercus texana and oak both are nouns.

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

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

Quercus texana: small deciduous tree having the trunk branched almost from the base with spreading branches; Texas and southern Oklahoma
oak: a deciduous tree of the genus Quercus; has acorns and lobed leaves

Other hypernyms of Quercus texana include oak tree.

Quercus texana (noun)	oak (noun)
small deciduous tree having the trunk branched almost from the base with spreading branches; Texas and southern Oklahoma	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