Definitions and terminology

When it existed previously, in 1968, the Vienna convention on road traffic gives one of the first international definition of a motor vehicle:

• (o) “Power-driven vehicle” means any self-propelled road vehicle, other than a moped in the territories of Contracting Parties which do not treat mopeds as motorcycles, and other than a rail-borne vehicle;

• (p) “Motor vehicle” means any power-driven vehicle which is normally used for carrying persons or goods by road or for drawing, on the road, vehicles used for the carriage of persons or goods. This term embraces trolley-buses, that is to say, vehicles connected to an electric conductor and not rail-borne. It does not cover vehicles, such as agricultural tractors, which are only incidentally used for carrying persons or goods by road or for drawing, on the road, vehicles used for the carriage of persons or goods
  — Vienna convention on road traffic

Other sources might provide other definitions, for instance in the year 1977, ISO 3833:1977 provide other definitions.