black hickory vs pignut hickory

black hickory and pignut hickory both are nouns.

Word	Noun	Adjective	Verb	Adverb
black hickory	Yes	No	No	No
pignut hickory	Yes	No	No	No

As nouns, black hickory and pignut hickory are synonyms defined as:

black hickory and pignut hickory: an American hickory tree having bitter nuts

Other synonyms of black hickory include brown hickory, Carya glabra, pignut.

black hickory (noun)	pignut hickory (noun)
an American hickory tree having bitter nuts	an American hickory tree having bitter nuts
smooth-barked North American hickory with 7 to 9 leaflets bearing a hard-shelled edible nut
North American walnut tree with hard dark wood and edible nut