Definition & Meaning of "compound locomotive"in English

What is a "compound locomotive"?

A compound locomotive is a type of steam locomotive that uses two or more sets of cylinders to improve efficiency. In this design, steam is used more than once, being released in multiple stages through different cylinders. This process reduces fuel consumption and increases power output, making compound locomotives more economical to operate compared to simpler designs. Compound locomotives were often used for hauling heavy trains over long distances, especially in the late 19th and early 20th centuries. The two most common types are the double-expansion and triple-expansion engines, depending on how many stages the steam goes through.