A crane is a machine that is capable of raising and lowering heavy objects and moving them horizontally. Cranes are distinguished from hoists, which can lift objects but that cannot move them sideways. Cranes are also distinguished from conveyors, that lift and move bulk materials, such as grain and coal, in a continuous process. The word crane is taken from the fact that these machines have a shape similar to that of the tall, long-necked bird of the same name.
A crane is a mechanical lifting device equipped with a winder, wire ropes, and sheaves that can be used to lift and lower materials and to move them horizontally. It uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of a human. Cranes are commonly employed in the transport industry for the loading and unloading of freight; in the construction industry for the movement of materials; and in the manufacturing industry for the assembly of heavy equipment.
Cranes exist in an enormous variety of forms, each tailored to a specific use. Sizes range from the small jib cranes used inside workshops to the tallest tower cranes used for constructing high-rise buildings, and the largest floating cranes used to build oil rigs and salvage sunken ships.