Automobiles are a type of motor vehicle for carrying passengers, built on four wheels with an internal combustion engine powered by fuel, most often gasoline (petrol). The term comes from the Greek prefix auto (“self”) and Latin word Mobilis (“mobile”), meaning “moving” or “able to move”. Cars are generally designed to offer people freedom of movement, enabling them to reach far away places in a relatively short time. However, the automobile can also have serious negative impacts on the environment, especially when used in cities where urban sprawl degrades landscapes and leads to traffic congestion. The resulting air pollution contributes to global climate change.

The automotive industry is a large, global business that encompasses a variety of sectors, including the design, production and operation of automobiles. It has grown to become one of the largest industries in the world, accounting for more than 5% of the gross domestic product (GDP) of most industrialized nations. The industry includes companies ranging from small specialty producers to large multinational giants.

Automakers design vehicles to meet a wide range of requirements and needs. These may include safety features like seat belts and airbags, comfort amenities, powertrain performance, size and weight, and aerodynamics or ways to reduce the friction of airflow around the car’s body. In addition, manufacturers must comply with regulations governing the control of pollutants produced by automobiles.

Most automobiles use a four-stroke internal combustion engine to propel them. The engine burns a liquid fuel such as gasoline, diesel or kerosene to generate the energy that turns the wheels of the car. This energy is transferred to the wheels by a transmission system. Different transmission systems use different gears to change the ratio of input to output, which affects how fast or slow the car can be driven.

Many types of automobiles are manufactured, ranging from small, fuel-efficient models to sports cars that can achieve high speeds. The selection of a front-wheel drive or rear-wheel drive model, the choice and arrangement of automobile components and the arrangement of those components to meet different purposes influence how well a particular model performs in any given situation or use.

The automobile’s ability to transport people in a closed, weather-protected compartment has made it an indispensable tool for modern life. In the United States alone, motorists travel more than three trillion miles (five trillion kilometres) each year. In addition to allowing individuals the freedom to go anywhere they wish, the automobile also makes it possible for many people to work from home or take a job on the road.

In addition, the automobile enables people to travel for pleasure, for example, to visit family and friends or to attend sporting events. People with limited resources can also buy used cars to save money. However, the rapid expansion of the automobile industry has led to environmental concerns and the development of alternative forms of transportation, such as trains, trams, buses and subways. Many countries have laws requiring the use of these alternatives for certain types of trips or to reduce congestion caused by automobiles.