1) Buckwheat family 2) Dicot family 3) Family polygonaceae 4) Magnoliopsid family 
The Polygonaceae are a family of flowering plants known informally as the knotweed family or smartweed—buckwheat family in the United States. The name is based on the genus Polygonum, and was first used by Antoine Laurent de Jussieu in 1789 in his book, Genera Plantarum. The name refers to the many swollen nodes the stems of some species have. I...
The only family of the buckwheat order of dicotyledonous flowering plants. It has 40 genera of herbs, shrubs, and trees. ... (12 Dec 1998) ... 
Polygonaceae is a family of herbaceous plants, characterised by the presence of an ochrea - a membranous sheath enclosing the stem at each of the joints, and bearing spikes or panicles of small flowers, often unisexual.
[n] - a family of plants of order Polygonales chiefly of the north temperate zone
family Polygonaceae noun a family of plants of order Polygonales chiefly of the north temperate zone; includes the buckwheats