The provinces of Vietnam are subdivided into second-level administrative units, namely districts (Vietnamese: huyện), provincial cities (thành phố trực thuộc tỉnh), and district-level towns (thị xã). The centrally-controlled municipalities (the other first-level division, in addition to provinces) are subdivided into rural districts (huyện), district-level towns, and urban districts (quận) that are further subdivided into wards (phường). The district (huyện) unit dates from the 15th century.