A tractor (from latin trahere) is a device intended for drawing, towing or pulling something which cannot propell itself.
Most commonly the word is used to describe a vehicle intended for such a task on some other vehicle or object.
Most common of these is a tractor designed for use on farms, typically a simple open vehicle with very large driving wheels and one seat, used for pulling agricultural machinery over rough ground, ploughing, harrowing and similar tasks. Most farm tractors have a means to transfer the engine's power to another machine such as a baler or reaper.
A less-well-used term is used to describe road tractors, which are heavy-duty vehicles with large engines and several axles. These tractors are designed to pull long road trailers, most often for the transport of freight of some kind over a significant distance (See Semi-trailer).
Of non-vehicles, a tractor is a part of printer that pulls the paper inside and pushes it outside of the printer.