Polygonum fagopyrum vs genus Polygonum

Polygonum fagopyrum and genus Polygonum both are nouns.

Word	Noun	Adjective	Verb	Adverb
Polygonum fagopyrum	Yes	No	No	No
genus Polygonum	Yes	No	No	No

Polygonum fagopyrum (noun)	genus Polygonum (noun)
a member of the genus Fagopyrum; annual Asian plant with clusters of small pinkish white flowers and small edible triangular seeds which are used whole or ground into flour	diverse genus of herbs or woody subshrubs of north temperate regions