buckwheat family vs family Polygonaceae

buckwheat family and family Polygonaceae both are nouns.

Word	Noun	Adjective	Verb	Adverb
buckwheat family	Yes	No	No	No
family Polygonaceae	Yes	No	No	No

As nouns, buckwheat family and family Polygonaceae are synonyms defined as:

buckwheat family and family Polygonaceae: a family of plants of order Polygonales chiefly of the north temperate zone; includes the buckwheats

Other synonyms of buckwheat family include Polygonaceae.

buckwheat family (noun)	family Polygonaceae (noun)
a family of plants of order Polygonales chiefly of the north temperate zone; includes the buckwheats	a family of plants of order Polygonales chiefly of the north temperate zone; includes the buckwheats