18-wheeler /ˌeɪtiːn-ˈwiːlər/ (or eighteen-wheeler)

(American) a very large truck (consisting of a tractor and a trailer) with nine wheels on each side, used especially for moving goods over long distances

It is called so for its total number of wheels: two front steering wheels on the tractor, plus dual wheels on each end of two axles (total of 8) at the rear of the tractor and supporting the front of the trailer, plus dual wheels on two axles at the rear of the trailer.

It is variously known as a transport in Canada; semi or single in Australia and New Zealand; semi, tractor-trailer, big rig, or eighteen-wheeler in the United States; and articulated lorry, abbreviated artic, in the United Kingdom, Ireland and New Zealand.


  • Research Questions:
  1. Find more words like 18-wheeler starting with a number & ending in -er. Why are they made like this? What is the meaning of –er in these words?
  2. Find more words like 18-wheeler ending in -er with a meaning other than “doer”. What are the meanings and functions of the suffix –er?
  3. What other kinds of trucks are there? How many wheels does each have? What other wheelers are there?