According to railroad terminology, how is a train defined?

The definition of a train in railroad terminology is specifically characterized as one or more engines that are coupled together, regardless of whether they are pulling cars. This definition highlights the fundamental role of the locomotive or engine in a train's operation. The inclusion of the phrase "with or without cars" emphasizes that even a single engine running alone is still classified as a train. This distinction is essential for understanding operational protocols and safety regulations within the railroad system, ensuring that the definition captures both freight and passenger train setups appropriately. This broad understanding of what constitutes a train is crucial for effective communication and management of train operations on the railway network.