nut

Nut is a term with several senses. In botany, a nut is a type of dry fruit with a hard, typically inedible outer shell that encloses a single seed. The shell is usually fused to the fruit wall and remains closed, even after ripening. True botanical nuts include chestnuts and hazelnuts. By contrast, many foods commonly called nuts are seeds of other fruits; almonds, pistachios, cashews, walnuts, and pecans are not true nuts in a strict sense, but are eaten and marketed as nuts.

Nuts are nutrient-dense, rich in fats—predominantly unsaturated fats—protein, fiber, and micronutrients such as vitamin E and magnesium. Because of their fat content, they are energy-dense and prone to rancidity if not stored properly.

Nuts grow on a variety of trees and shrubs in warm temperate and tropical regions. Major producers include China, the United States, India, Vietnam, Italy, and Turkey. Harvested nuts are usually dried, sometimes roasted or salted, and processed into products such as nut butters, oils, or confectionery ingredients.

In nutrition and cooking, nuts are valued for flavor and texture but can trigger severe allergic reactions in some people; guidance on handling and labeling is common, especially for packaged foods. For storage, keeping nuts in a cool, dry place—ideally refrigerated or frozen for long-term storage—helps preserve quality.

In addition to the edible sense, 'nut' also refers to a hardware fastener: a metal or polymer piece with internal threads that mates with a bolt or screw. Common types include hex nuts, lock nuts, and wing nuts.