pignut hickory vs hickory

pignut hickory and hickory both are nouns.

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

As nouns, hickory is a hypernym of pignut hickory; that is, hickory is a word with a broader meaning than pignut hickory:

Other hypernyms of pignut hickory include hickory tree.

pignut hickory (noun)	hickory (noun)
an American hickory tree having bitter nuts	American hardwood tree bearing edible nuts
	valuable tough heavy hardwood from various hickory trees