Engine power in the context of Engine downsizing

Power-to-weight ratio (PWR, also called specific power, or power-to-mass ratio) is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measurement of actual performance of any engine or power source. It is also used as a measurement of performance of a vehicle as a whole, with the engine's power output being divided by the weight (or mass) of the vehicle, to give a metric that is independent of the vehicle's size. Power-to-weight is often quoted by manufacturers at the peak value, but the actual value may vary in use and variations will affect performance.

The inverse of power-to-weight, weight-to-power ratio (power loading) is a calculation commonly applied to aircraft, cars, and vehicles in general, to enable the comparison of one vehicle's performance to another. Power-to-weight ratio is equal to thrust per unit mass multiplied by the velocity of any vehicle.

A battery electric vehicle (BEV), pure electric vehicle, only-electric vehicle, fully electric vehicle or all-electric vehicle is a type of electric vehicle (EV) that uses electrical energy exclusively from an on-board battery pack to power one or more electric traction motors, on which the vehicle solely relies for propulsion.

This definition excludes hybrid electric vehicles (HEVs; including mild, full and plug-in hybrids), which use internal combustion engines (ICEs) in adjunct to electric motors for propulsion; and fuel cell electric vehicles (FCEVs) and range-extended electric vehicles (REEVs), which consume fuel through a fuel cell or an ICE-driven generator to produce electricity needed for the electric motors. BEVs have no fuel tanks and replenish their energy storage by plugging into a charging station, electrical grid or getting a new battery at a battery swap station, and use motor controllers to modulate the output engine power and torque, thus eliminating the need for clutches, transmissions and sophisticated engine cooling as seen in conventional ICE vehicles. BEVs include – but are not limited to – all battery-driven electric cars, buses, trucks, forklifts, motorcycles and scooters, bicycles, skateboards, railcars, boat and personal watercraft, although in common usage the term usually refers specifically to passenger cars.

A bank engine (United Kingdom/Australia) (colloquially a banker), banking engine, helper engine or pusher engine (North America) is a railway locomotive that temporarily assists a train that requires additional power or traction to climb a gradient (or bank). Helpers/bankers are most commonly found in mountain divisions (called "helper districts" in the United States), where the ruling grade may demand the use of substantially greater motive power than that required for other grades within the division.

A V12 engine is a twelve-cylinder piston engine where two banks of six cylinders are arranged in a V configuration around a common crankshaft. V12 engines are more common than V10 engines. However, they are less common than V8 engines.

The first V12 engine was built in 1904 for use in racing boats. Due to the balanced nature of the engine and the smooth delivery of power, V12 engines were found in early luxury automobiles, boats, aircraft, and tanks. Aircraft V12 engines reached their apogee during World War II, after which they were mostly replaced by jet engines. In Formula One racing, V12 engines were common during the late 1960s and early 1990s.

In aviation, assisted takeoff is any external system for helping aircraft (more specifically fixed-wing aircraft) to become airborne (take off) for flight, as opposed to doing so conventionally using strictly their own propulsion. The reasons assistance might be needed include: the combined weight of the aircraft and its payloads exceeding the maximum takeoff weight; insufficient engine power by design or malfunction, insufficient available runway length (such as on the flight deck of an aviation warship), or a combination of the above. Assisted takeoff is also required for gliders, which do not have any engine and thus are unable to propel themselves for takeoffs.

In a motor vehicle, the powertrain comprises the main components that generate power and deliver that power to the road surface, water, or air. This includes the engine, transmission, drive shafts, differentials, and the final drive (drive wheels, continuous track as in military tanks or caterpillar tractors, propeller, etc.). Hybrid powertrains also include one or more electric traction motors that operate to drive the vehicle wheels. All-electric vehicles ("electric cars") eliminate the engine altogether, relying solely on electric motors for propulsion. Occasionally the term powerplant is casually used to refer to the engine or, less often, the entire powertrain.

A motor vehicle's driveline or drivetrain consists of the parts of the powertrain excluding the engine. It is the portion of a vehicle, after the prime mover, that changes depending on whether a vehicle is front-wheel, rear-wheel, or four-wheel drive, or less-common six-wheel or eight-wheel drive.