A doughnut (also spelled donut) is a sweet, fried piece of dough shaped like a ring with a hole in the middle, or sometimes as a filled ball. The ring shape serves a practical purpose: it helps the dough cook evenly all the way through. Before bakers started making the hole, the centers of fried dough often stayed raw and doughy while the outside burned.

Doughnuts became popular in America in the 1800s, and today they're enjoyed around the world, glazed with sugar, covered in chocolate, filled with jelly or cream, or topped with colorful sprinkles. Police officers eating doughnuts became such a common sight in mid-20th century America (partly because doughnut shops stayed open late when little else did) that doughnuts and police became linked in popular culture.

The word also describes the shape itself. Scientists sometimes compare the spinning cloud of gas and dust around a black hole to a doughnut, and when you spin your car in a tight circle, leaving circular tire marks on the pavement, you're doing doughnuts (though this is dangerous and illegal on public roads).