Source:http://linkedlifedata.com/resource/umls/id/C0028723
MSH: Botanically, a type of single-seeded fruit in which the pericarp enclosing the seed is a hard woody shell. In common usage the term is used loosely for any hard, oil-rich kernel. Of those commonly eaten, only hazel, filbert, and chestnut are strictly nuts. Walnuts, pecans, almonds, and coconuts are really drupes. Brazil nuts, pistachios, macadamias, and cashews are really seeds with a hard shell derived from the testa rather than the pericarp.,NCI: A dry, indehiscent, hard, one-seeded simple fruit, generally produced from a gynoecium of more than one fused carpel.,NCI: In botany, it is a simple dry fruit with one seed (rarely two) in which the ovary wall becomes very hard (stony or woody) at maturity, and where the seed remains unattached or unfused with the ovary wall. Most nuts come from pistils with inferior ovaries and all are indehiscent (not opening at maturity). True nuts are produced by some plants-- families of the order Fagales, including Juglandaceae, Fagaceae, and Betulaceae. (from Wikipedia)