A gadget is a device that has a useful specific practical purpose and function. Gadgets tend to be more unusual or cleverly designed than normal technology. In some circles the distinction between a gadget and a gizmo is that a gizmo has moving parts, whereas a gadget need not have them. For example, a nifty digital watch would be a gadget, while an analog watch would be a gizmo.

In contrast, a device of clever design that has no practical purpose is called a novelty item.

The etymology of the word gadget is disputed. Some sources say it was "invented" when Gaget, Gauthier & Cie, the company behind the casting of the Statue of Liberty, made a small-scale version of the monument and named it after their firm. Other sources cite a derivation from sailors' terminology; the French gâchette which has been applied to various pieces of a firing mechanism; the French gagée, a small tool or accessory; the French engager, to engage one thing with another; or even a diminutive of the Scottish engineering jargon gadge, a form of measuring device. The spring-clip used to hold the base of a vessel during glass-making is also known as a gadget.