Quercus montana vs chestnut oak

Quercus montana and chestnut oak both are nouns.

Word	Noun	Adjective	Verb	Adverb
Quercus montana	Yes	No	No	No
chestnut oak	Yes	No	No	No

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

Quercus montana: medium to large deciduous tree of the eastern United States; its durable wood is used as timber or split and woven into baskets or chair seats
chestnut oak: an oak having leaves resembling those of chestnut trees

Quercus montana (noun)	chestnut oak (noun)
medium to large deciduous tree of the eastern United States; its durable wood is used as timber or split and woven into baskets or chair seats	an oak having leaves resembling those of chestnut trees