The S-train is a type of hybrid urban-suburban rail serving a metropolitan region. Some of the larger S-train systems provide service similar to rapid transit systems, while smaller ones often resemble commuter or even regional rail. They are especially common in Germany and Austria, where they are known as S-Bahn, which in the 1930s was an abbreviation of either Schnellbahn, Stadtbahn or Stadtschnellbahn, depending on the city, but they must not be confused with U-Stadtbahnen. Similar S-train systems exist also in Switzerland known as S-Bahn as well. In Denmark, they are known as S-tog [ˈesˌtsʰɔˀw], in the Czech Republic as Esko or S-lines, and northern Italy as Servizio ferroviario followed by either the word "metropolitano" (in Turin) or "suburbano" (in Milan).