Nut (fruit)
A nut is a dry, indehiscent fruit with a hard wall enclosing a single seed. In botanical usage, many foods called nuts are not true nuts.
Fruit: The mature ovary of a flowering plant, usually containing seeds. A nut is one specific kind of fruit, defined by its mature ovary wall.
Pollination: The transfer of pollen to a flower's stigma or to a seed plant's ovule-bearing structure. Pollination enables fertilization that initiates nut development.
Caryopsis: A dry, one-seeded fruit whose thin pericarp is fused to the seed coat. Unlike a nut, a caryopsis has fruit wall fused to its seed coat.
Acorn: The fruit of an oak, consisting of a single seed partly enclosed by a cup-like cupule. An acorn is a familiar example of a true botanical nut.
Nut allergy: An immune reaction to proteins in particular nuts or nut-like foods. Allergy labels often group foods by culinary use rather than botanical fruit type.
Pericarp: The wall of a fruit, developed from the ovary wall after fertilization. Its hard, dry pericarp forms the defining shell of a nut.
Fertilization in plants: The fusion of plant gametes that produces a zygote and initiates seed formation. It produces the embryo inside the developing nut's seed.
Achene: A dry, indehiscent, one-seeded fruit whose pericarp is not fused to the seed coat. An achene resembles a nut but usually has a thinner, less woody wall.
Hazelnut: The edible fruit of hazel trees, enclosed in a hard shell. A hazelnut is a true nut with a hard pericarp around one seed.
Tree nut: A culinary and regulatory category of edible nuts and seeds that grow on trees. The food category includes items that are not botanical nuts.