The wheels which actually drive the vehicle along. In the case of a steam engine these will be the large wheels in the middle of the locomotive connected together by coupling rods. They may sometimes have smaller wheels either in front of behind them - see wheel arrangements for more details.
Wheel that transmits motion and force, by receiving power from the engine by means of the connecting rod.
It is the wheel that not only supports the vehicle but also moves it because it is connected to the propulsion engine elements. A drive wheel can also be the leading wheel.
The main wheel which communicates motion to another or others.
a wheel that drives a motor vehicle (transforms torque into a tractive force)
Any wheel connected to the locomotive's pistons, and which therefore drives the train. British classification of wheel arrangements on steam locomotives uses a X-Y-Z format where X=the leading carrying wheels, Y=the driving wheels and Z=the trailing carrying wheels. A 2-4-0 wheel arrangement therefore describes a locomotive that has one leading wheel, two driving wheels (coupled) and no trailing wheel on each side of the locomotive.
On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotive's pistons (or turbine, in the case of a steam turbine locomotive). On a conventional, non-articulated locomotive, the driving wheels are all coupled together with side rods (also known as coupling rods); normally one pair is directly driven by the main rod (or connecting rod) which is connected to the end of the piston rod; power is transmitted to the others through the side rods.