Semi-trucks are sometimes called other names, including big rig, semis, or 18-wheelers, and for the last moniker, this is because of the combined number of wheels of both the tractor and the trailer.

Semi-trucks are crucial for getting goods across the U.S., and in 2022, semis achieved $940.8 billion in freight revenue, per TruckInfo.net.

The reason semi-trucks are also called tractor trailers comes down to how they're built. A typical setup includes two main parts: The tractor in front, which houses the engine and driver, and the ...