The term 'Train Unit' is composed of four different components: Railcar (7 letters), CAR (3 letters), BOXCAR (6 letters), and Daycoach (8 letters). A railcar is a wheeled vehicle used for transporting goods or passengers on a railway. A CAR is a wheeled vehicle, typically with four wheels, powered by an engine and used for transportation. A BOXCAR is a type of railroad CAR that is enclosed and usually used to transport freight. Finally, a daycoach is a type of passenger CAR used on short-distance trains. Together, these four components make up a train unit, which is a complete set of cars used to transport passengers or freight.