Nuttall's oak vs oak

Nuttall's oak and oak both are nouns.

Word	Noun	Adjective	Verb	Adverb
Nuttall's oak	Yes	No	No	No
oak	Yes	No	No	No

As nouns, oak is a hypernym of Nuttall's oak; that is, oak is a word with a broader meaning than Nuttall's oak:

Nuttall's oak: similar to the pin oak; grows in damp sites in Mississippi River basin
oak: a deciduous tree of the genus Quercus; has acorns and lobed leaves

Other hypernyms of Nuttall's oak include oak tree.

Nuttall's oak (noun)	oak (noun)
similar to the pin oak; grows in damp sites in Mississippi River basin	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