The almond (Prunus amygdalus, syn. Prunus dulcis) is a tree native to Iran and surrounding countries but widely cultivated elsewhere. The almond is also the name of the edible and widely cultivated seed of this tree. The genus Prunus is classified with the peach in the subgenus Amygdalus, distinguished from the other subgenera by corrugations on the shell (endocarp) surrounding the seed. The fruit of the almond is a drupe, consisting of an outer hull and a hard shell with the seed, which is not a true nut inside. Shelling almonds refers to removing the shell to reveal the seed. Almonds are sold shelled or unshelled. Blanched almonds are shelled almonds that have been treated with hot water to soften the seedcoat, which is then removed to reveal the white embryo.
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.