An automobile, or motor vehicle, is a self-propelled wheeled passenger transport that uses an internal combustion engine fueled by gasoline (petrol) or other petroleum fuel. It is one of the world’s most common modern technologies, and it is a cornerstone of one of the world’s largest industries.

Modern automobiles use a water-cooled piston-type internal combustion engine, usually mounted at the front of the vehicle, to drive one or more wheels. Power is transmitted by a system of gears and axles, which may include a differential and clutch assembly. In most cases, the engines are powered by gasoline; however, diesel engines—which burn a heavier fuel oil—are used in some buses and trucks and, more recently, in a small number of family sedans.

Automobiles radically transformed twentieth-century America, as they became the backbone of a new consumer goods-oriented society and one of the country’s primary sources of economic growth. They spawned dozens of spin-off industries, including steel and petroleum manufacturing, and revolutionized the transportation industry. They also helped transform American landscapes and culture, by enabling people to live farther apart than ever before and travel great distances with ease.

The automobile has become one of the most popular and important of human inventions, with about 1.4 billion vehicles in operation worldwide. In addition to delivering many conveniences, cars can save time and money, provide independence from public transport, and open up new possibilities for work and play. As technology advances, manufacturers are working to develop semiautonomous and autonomous vehicles that can take over some of the driver’s tasks.