The hazelnut is the fruit of the hazel and therefore includes any of the nuts deriving from species of the genus Corylus, especially the nuts of the species Corylus avellana. They are also known as cobnuts or filberts according to species. A cob is roughly spherical to oval, about 15–25 mm long and 10–15 mm in diameter, with an outer fibrous husk surrounding a smooth shell and a filbert that is more elongated, being about twice as long as its diameter. Hazelnuts are rich in protein, monounsaturated fat, vitamin E, manganese, and numerous other essential nutrients.

Nuts

A nut is a fruit composed of a hard shell and a seed, which is generally edible.

There is an additional requirement in botany that the shell does not open to release the seed (indehiscent). In a general context, a wide variety of dried seeds are called nuts, but in a botanical context, only ones that include the indehiscent fruit are considered true nuts.