A single-decker bus or single-deck bus, is a bus that has a single deck for passengers. Normally the use of the term single-decker refers to a standard two-axled rigid bus, in direct contrast to the use of the term double-decker bus, which is essentially a bus with two passenger decks and a staircase. These types of single-deckers may feature one or more doors, and varying internal combustion engine, battery and electric motor positions. The majority of single-deckers have a length of up to 12 m, although some exceptions of longer buses exist. They also typically weigh between 11 and 14 t.