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A peanut, also known as a groundnut, is the fruit of Arachis hypogaea, a plant in the family Fabaceae. The peanut is classed as a grain legume rather than as a botanical nut, although in culinary and colloquial use it is generally treated as one. Uses of peanuts include consumption as a snack and in various dishes, peanut butter, and – due to its high oil content – as a vegetable oil. Peanuts cause allergic reactions in some humans. Clockwise from top left, this photograph shows a peanut with its shell cracked open, a whole unshelled peanut, an unpeeled peanut seed, a halved peeled seed, and a whole peeled seed. This picture was focus-stacked from 31 separate images.Photograph credit: Ivar Leidus