It referred to a former princedom or duchy, which was unified with the Polish Kingdom, and lost its political sovereignty, but retained its hierarchy of officials and bureaucracy.
From around the 14th century some of the former princedoms, now ziemias, were assigned to officials known as voivodes and became primary units of administration known as voivodeships (provinces).
Over subsequent centuries, ziemias became increasingly integrated into their voivodeships and lost most of their autonomy.
Currently, the term ziemia may apply to any area, historic or not, which is located around a main town or city.
In Ukraine the term was intended to be introduced by Mykhailo Hrushevskyi in Ukraine as part of the administrative reform in 1918 which was interrupted by the Pavlo Skoropadskyi coup in April of that year.