The term multiple unit or MU is used to describe a self-propelled carriages capable of coupling with other units of the same or similar type and still being controlled from one driving cab. The term is commonly used to denote passenger trainsets consisting of more than one carriage. Single self-propelling carriages (also called railcar

Railcar

A railcar, in British English and Australian English, is a self-propelled railway vehicle designed to transport passengers. The term "railcar" is usually used in reference to a train consisting of a single coach , with a driver's cab at one or both ends. Some railways, e.g., the Great Western...

s, rail motor coach

Rail motor coach

A motor coach or motorcar is a powered rail vehicle able to pull several trailers and at the same time transport passengers or luggage. With multiple unit train control, one operator can control several “motor coaches” efficiently in the same train, making longer trains possible, it can be part of...

es or railbus

Railbus

A railbus is a very lightweight type passenger rail vehicle that shares many aspects of their construction with a bus, usually having a bus, or modified bus body, and having four wheels on a fixed base, instead of on bogies...

es) can be referred to as multiple units if capable of operating with other units.

Multiple units are classified by their power source and are of two main types: electric multiple unit

Electric multiple unit

An electric multiple unit or EMU is a multiple unit train consisting of self-propelled carriages, using electricity as the motive power. An EMU requires no separate locomotive, as electric traction motors are incorporated within one or a number of the carriages...

 (EMU) or diesel multiple unit

Diesel multiple unit

A diesel multiple unit or DMU is a multiple unit train consisting of multiple carriages powered by one or more on-board diesel engines. They may also be referred to as a railcar or railmotor, depending on country.-Design:...

 (DMU).