The Zürich S-Bahn system is a network of rail lines that has been incrementally expanded to cover the ZVV area, which comprises the entire canton of Zürich and portions of neighboring cantons (Aargau, Schaffhausen, Schwyz, Thurgau and St. Gallen), with a few lines extending into Germany. The network is one of many commuter rail operations in German speaking countries to be described as an S-Bahn.