Main Difference
The main difference between Hazelnut and Chestnut is that the Hazelnut is a nut of the hazel tree and Chestnut is a genus of plants.
Hazelnut
The hazelnut is the nut 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. It also is known as cobnut or filbert nut according to species. A cob is roughly spherical to oval, about 15–25 mm (0.59–0.98 in) long and 10–15 mm (0.39–0.59 in) in diameter, with an outer fibrous husk surrounding a smooth shell. A filbert is more elongated, being about twice as long as its diameter. The nut falls out of the husk when ripe, about 7 to 8 months after pollination. The kernel of the seed is edible and used raw or roasted, or ground into a paste. The seed has a thin, dark brown skin, which sometimes is removed before cooking.
Hazelnuts are used in confectionery to make praline, and also used in combination with chocolate for chocolate truffles and products such as Nutella and Frangelico liqueur. Hazelnut oil, pressed from hazelnuts, is strongly flavoured and used as a cooking oil. Turkey is the world’s largest producer of hazelnuts.
Hazelnuts are rich in protein, monounsaturated fat, vitamin E, manganese, and numerous other essential nutrients (nutrition table below).
Chestnut
The chestnuts are a group of eight or nine species of deciduous trees and shrubs in the genus Castanea, in the beech family Fagaceae. They are native to temperate regions of the Northern Hemisphere.
The name also refers to the edible nuts they produce.
Hazelnut (noun)
The fruit of the hazel tree.
Chestnut (noun)
A tree or shrub of the genus Castanea.
Chestnut (noun)
The nut of this tree or shrub.
Chestnut (noun)
A dark, reddish-brown colour/color.
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Chestnut (noun)
A reddish-brown horse.
Chestnut (noun)
The wood of a chestnut tree.
Chestnut (noun)
(Often “old chestnut”) An old joke; a worn-out meme, phrase, ploy, etc. so often repeated as to have grown tiresome or ineffective.
Chestnut (noun)
A round or oval horny plate found on the inner side of the leg of a horse or other animal, similar to a birthmark on a human.
Chestnut (noun)
horse-chestnut
Chestnut (adjective)
Of a deep reddish-brown colour, like that of a chestnut.
Chestnut (noun)
a glossy hard brown edible nut which develops within a bristly case and which may be roasted and eaten.
Chestnut (noun)
a deep reddish-brown colour
“chestnut hair”
Chestnut (noun)
a horse of a reddish-brown or yellowish-brown colour, with a brown mane and tail
“a chestnut stallion”
Chestnut (noun)
the large European tree that produces the edible chestnut, with serrated leaves and heavy timber.
Chestnut (noun)
short for horse chestnut
Chestnut (noun)
used in names of trees and plants that are related to the sweet chestnut, or produce similar nuts or edible parts that resemble them, e.g. water chestnut.
Chestnut (noun)
a small horny patch on the inside of each of a horse’s legs.