Is buckwheat a grain

No. It isn't. It's two entirely different plants.

Don't let the Word 'wheat' in it's name confuse you. Buckwheat (Fagopyrum esculentum) looks like a grain and tastes like a grain but isn't a grain at all. Buckwheat is thought of as a cereal, but is actually an herb of the buckwheat family, Polygonaceae, a relative of the rhubarb. Buckwheat is also gluten free, which makes it an ideal food for those allergic or sensitive to the gluten in found wheat and other true grains. After being removed from the husk, the triangular seeds are used to make flour. --------