. . "A semi-trailer truck is the combination of a tractor unit and one or more semi-trailers to carry freight. It is variously known as a transport (truck) in Canada; semi or single in Australia; semi, tractor-trailer, big rig, or eighteen-wheeler in the United States; articulated lorry, abbreviated artic, in Britain and Ireland.A semi-trailer attaches to the tractor with a fifth wheel hitch, with much of its weight borne by the tractor."@en . . .