I was wondering why semi-trucks are called that. Doesn’t semi mean “part of”? A semi-truck is a whole truck if I ever saw one!
Semi truck or semi is short for semi-trailer truck.¹ The prefix semi- literally means half.² The term describes a truck consisting of a tractor and a semi-trailer. A semi-trailer is semi-supported (half supported) by its own wheels, which support only the rear of the trailer. The front of the trailer is supported by the rear wheels of the tractor.³