noun, plural: nuts
The fruits produced by angiosperms (flowering plants) may be grouped in many ways. One of which is to categorize fruits as either fleshy or dry. A fleshy fruit is one in which part or all of the pericarp is fleshy at maturity. These are exemplified by berries and drupes. A dry fruit is, in contrast, not fleshy and the pericarp layers (i.e. epicarp, mesocarp, and endocarp) are hardly distinguishable. Dry fruits may further be grouped as dehiscent, indehiscent, or schizocarpic. A dehiscent fruit is one that splits open when ripe. An indehiscent fruit does not split open even when the seeds reach maturity. A schizocarpic fruit is intermediate by being indehiscent and capsular at the same time.
A nut is a dry indehiscent fruit with a single seed. The pericarp is a hard shell, which may be woody or leathery. The seed is free, i.e. unattached to the pericarp. The fruit develops from a uniovuled ovary in a simple or compound pistil. Most nuts develop from pistils with inferior ovaries. Examples of nuts are wingnut, beech, oak, stone oak, alder, birch, hornbeam, chestnut, and hazelnut.
Many culinary nuts are not true nuts. In botanical context, a true nut is an indehiscent fruit. It means the seed (kernel) is not released through dehiscence. Furthermore, the fruit forms a hard shell when ripe and are found on trees. In culinary, a nut pertains to any large, oily edible kernel within a shell. Some of the culinary nuts not considered as true nuts in botanical sense are almonds (the seed of a drupe), brazil nut (the seed from a capsule), cashew (the seed of a drupe with accessory tissues), macadamia (the kernel of a follicle), pecan ( the seed of a drupe), peanut (the seed of a legume), pine nut (the seed of certain coniferous trees), pistachio (the seed of the drupe), walnut (the seed of the drupe), etc.