Unitary Government

the system of government in which most power is held within the central government.

( one central government has power over weaker states, and power is not shared between individual states. )

Example

United Kingdom

The United Kingdom is both a parliamentary democracy and constitutional monarchy. The head of state is the current king or queen, while the head of government is the prime minister. The United Kingdom is an "asymmetrically decentralised unitary state" ( meaning that control is mantained by local offices, but unevenly throughout different areas) , made up of England and 3 other countries with devolved government ( those countries being Scotland, Wales and Northern Ireland ). Though, the UK Parliament itself keeps absolute sovereignty, the Scottish and Welsh parliament and the Northern Ireland Assembly have obtained varying degrees of government power since devolution in 1999.

tl;dr : the UK is a unitary government, though devolution exists.