A unitary authority is a type of local authority that has a single tier and is responsible for all local government functions within its area or performs additional functions which elsewhere in the relevant country are usually performed by national government or a higher level of sub-national government. Typically unitary authorities cover towns or cities which are large enough to function independently of county or other regional administration. Sometimes they consist of national sub-divisions which are distinguished from others in the same country by having no lower level of administration.