What is another word for underground trains?
Pronunciation: [ˌʌndəɡɹˈa͡ʊnd tɹˈe͡ɪnz] (IPA) 
Underground trains, or subways, are a form of rapid transit that run through tunnels below a city. There are several different synonyms that can be used to describe this type of transportation, such as metro, tube, subway system, rapid transit system, and underground railway. These words are often used interchangeably to describe the same type of transportation system, but they can also have specific regional connotations. For example, in London, the Underground is commonly referred to as the "Tube" because of the cylindrical shape of the tunnels. Regardless of what term is used, underground trains are an important and efficient way for millions of people in cities around the world to get around every day.
