A diner is a type of restaurant found across the United States and Canada, as well as parts of Western Europe and Australia. Diners offer mostly American cuisine, a casual atmosphere, and, typically, a combination of booths served by a waitstaff and a long sit-down counter with direct service, in the smallest simply by a cook. Many diners have extended hours, and some along highways and areas with significant shift work stay open for 24 hours.
Considered quintessentially American, many diners share an archetypal exterior form. Some of the earliest were converted rail dining cars, retaining their streamlined structure and interior fittings. From the 1920s to the 1940s, diners, by then commonly known as "lunch cars", were usually prefabricated in factories, like modern mobile homes, and delivered on site with only the utilities needing to be connected. As a result, many early diners were typically small and narrow to fit onto a rail car or truck. This small footprint also allowed them to fit into tiny and relatively inexpensive lots that were unable to support a larger enterprise. Diners were historically small businesses operated by the owner, with some presence of restaurant chains evolving over time.