Walnut

A walnut is a nut from a walnut tree.

It also refers to a type of wood from the same tree, sometimes used in construction.

Walnuts are edible and can be pressed for their oil, which has a very high ratio of good fats (omega-3, polyunsaturated) to bad fats (saturated). It can be used in frying, but should not be exposed to heat for too long, as it can develop a bitter taste.