bitter hickory vs bitternut hickory

bitter hickory and bitternut hickory both are nouns.

Word	Noun	Adjective	Verb	Adverb
bitter hickory	Yes	No	No	No
bitternut hickory	Yes	No	No	No

As nouns, bitter hickory and bitternut hickory are synonyms defined as:

bitter hickory and bitternut hickory: hickory of the eastern United States having a leaves with 7 or 9 leaflets and thin-shelled very bitter nuts

Other synonyms of bitter hickory include bitter pignut, bitternut, Carya cordiformis, swamp hickory.

bitter hickory (noun)	bitternut hickory (noun)
hickory of the eastern United States having a leaves with 7 or 9 leaflets and thin-shelled very bitter nuts	hickory of the eastern United States having a leaves with 7 or 9 leaflets and thin-shelled very bitter nuts