Semi truck

A semi-trailer truck is a large vehicle that consists of a towing engine, known as a tractor in the United States and truck in many other places, attached to one or more semi-trailers to carry freight. It is also known as a transport (truck) in Canada; prime mover in Australia; semi, tractor-trailer, big rig, or 18-wheeler in the United States; and articulated lorry, abbreviated artic, in Britain and Ireland. A semi-trailer does not trail completely behind the towing vehicle, but is attached at a point that is just forward of the rear-most axle of the towing unit. This is done so that a large portion of the weight of the trailer is carried by the prime mover. This arrangement means that both tractor and semi-trailer will have a distinctly different design than a rigid truck and trailer. [Semi-trailer truck. Wikipedia]