rim

Rim is the outer edge or border of a circular object, or the lip encircling an opening. It defines the boundary of the inner space and often provides support or a grip. The term comes from Old English rimm, meaning edge, with cognates in other Germanic languages.

In mechanical engineering and transportation, the rim refers to the outer hoop of a wheel to which the tire is mounted. Rims are made from steel, aluminum alloys, or carbon fiber and are specified by diameter, width, and bolt pattern; rim design affects stiffness, weight, and performance.

In tableware and cookware, the rim is the outer edge of plates, bowls, cups, and saucers. Rims can be plain or decorated, and on some items the rim shape helps with handling or pouring.

In geology and planetary science, crater rims are the circular boundaries formed by impacts or volcanic collapse. The rim's height and ruggedness yield clues about the impact energy and subsequent erosion.

In sports, the basketball rim is the fixed metal ring through which players aim to shoot the ball; it is mounted to the backboard at a standardized height, and includes a net in many games.

In other contexts, rims appear around containers, openings, and frames, such as the rim of a glass, a sink, or a window, serving to define edges, guide assembly, or protect the interior.

See also: edge, border, lip, circumference.