Ohio buckeye vs horse chestnut

Ohio buckeye and horse chestnut both are nouns.

Word	Noun	Adjective	Verb	Adverb
Ohio buckeye	Yes	No	No	No
horse chestnut	Yes	No	No	No

As nouns, horse chestnut is a hypernym of Ohio buckeye; that is, horse chestnut is a word with a broader meaning than Ohio buckeye:

Ohio buckeye: a buckeye with scaly grey bark that is found in the central United States
horse chestnut: tree having palmate leaves and large clusters of white to red flowers followed by brown shiny inedible seeds

Other hypernyms of Ohio buckeye include Aesculus hippocastanum, buckeye.

Ohio buckeye (noun)	horse chestnut (noun)
a buckeye with scaly grey bark that is found in the central United States	tree having palmate leaves and large clusters of white to red flowers followed by brown shiny inedible seeds
	the inedible nutlike seed of the horse chestnut