18-wheeler

An 18-wheeler is a large commercial truck commonly known as a semi-truck or tractor-trailer. It consists of a tractor unit that provides power and pulls a trailer for cargo. The "18 wheels" refer to the total number of wheels on both the tractor and the trailer, which typically has 10 wheels on the tractor and 8 on the trailer. These vehicles are essential for long-distance freight transport, enabling efficient movement of goods across highways. They require specialized licensing, maintenance, and driver training due to their size, weight, and complexity.