When ultimate authority rests in a single central government that may create or abolish regional units at will, the state is unitary. Regional and local governments exercise only delegated powers.

Most of the world’s states are unitary, including France, Japan, and the United Kingdom (despite recent devolution). Centralization can produce uniform standards and simpler accountability. It can also neglect regional diversity and overload the center with decisions better made locally.

Unitary states sometimes devolve substantial authority without becoming federations, because the center retains the legal right to reclaim power. Political practice may make devolution difficult to reverse even when constitutional theory allows it. The choice between unitary and federal design reflects history, size, diversity, and the preferences of those who write constitutions.

• Single central authority holds ultimate power
• Regional powers are delegated, not constitutionally entrenched
• Common form of state organization worldwide
• Can still include significant administrative decentralization