pignut vs pignut hickory

pignut and pignut hickory both are nouns.

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

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

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

pignut (noun)	pignut hickory (noun)
an American hickory tree having bitter nuts	an American hickory tree having bitter nuts