A unitary state is a state or country that is governed constitutionally as one single unit, with one constitutionally created legislature. The term is the antonym of federation. Governmental power may well be transferred to lower levels, to regionally or locally elected assemblies, governors and mayors ("devolved government"), but in a unitary state the central government has the principal right to recall such delegated power.
In federal systems, assemblies in those states composing the federation have a constitutional existence and a set of constitutional functions which cannot be unilaterally changed by the central government. In some such cases, such as in the United States, it is the federal government that has only those powers specifically delegated to it. In a unitary state, by contrast, any sub-governmental units can be created or abolished, and have their powers varied, by the central government. The process in which sub-government units and/or regional parliaments are created by a central government is known as devolution. A unitary state can broaden and narrow the functions of such devolved (sub-)governments without formal agreement from the affected bodies.
The United Kingdom is a particularly striking example of a unitary state with a series of parliament-created devolved assemblies, for Scotland, Wales and Northern Ireland, all of which were created in between 1998 and 1999. The Republic of Ireland may be given as an example of the opposite, a unitary state lacking subnational governments.
Some states are hybrids between the federal and unitary models. An example of this would be Australia, which is federal with respect to the six states (New South Wales, Queensland, South Australia, Tasmania, Victoria and Western Australia) that have their own constitutional existence, but unitary with respect to the two mainland territories (the Northern Territory and the Australian Capital Territory), whose governments exercise similar powers to the states but by virtue of delegation of powers from the national government.
Most federal states also have unitary lower levels of government. Thus while the United States itself is federal, most (if not all) U.S. states are themselves unitary, with counties and other municipalities having only the authority given (devolved) to them by the state constitution or legislature.
List of unitary states