(countable) Under the Whyte notation system, a steam locomotive that has a four-wheel leading truck, one powered driving axle and a four-wheel unpowered trailing truck.

Under the Whyte notation system, a steam locomotive with four leading wheels in a leading truck, fourteen driving wheels (seven axles) in a rigid frame, and four trailing wheels in a trailing truck.

Under the Whyte notation, a steam locomotive that has four coupled driving wheels followed by four trailing wheels, with no leading wheels.

Under the Whyte notation system, a steam locomotive that has four leading wheels arranged in a leading truck, eight coupled driving wheels and four trailing wheels in a trailing truck.

Under the Whyte notation system, a steam locomotive that has two leading wheels arranged in a leading truck, four coupled driving wheels and four trailing wheels in a trailing truck.

Under the Whyte notation system, a steam locomotive that has four leading wheels arranged in a leading truck, six coupled driving wheels and four trailing wheels in a trailing truck.

Under the Whyte notation system, a steam locomotive that has four leading wheels on a leading truck followed by two sets of coupled driving wheels, and no trailing wheels.

plural of 4-4-4

plural of 4-4-0

plural of 4-4-2