dwarf oak vs chestnut oak

dwarf oak and chestnut oak both are nouns.

Word	Noun	Adjective	Verb	Adverb
dwarf oak	Yes	No	No	No
chestnut oak	Yes	No	No	No

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

dwarf oak: deciduous shrubby tree of northeastern and central United States having a sweet edible nut and often forming dense thickets
chestnut oak: an oak having leaves resembling those of chestnut trees

dwarf oak (noun)	chestnut oak (noun)
deciduous shrubby tree of northeastern and central United States having a sweet edible nut and often forming dense thickets	an oak having leaves resembling those of chestnut trees