Decentralisation of power is a feature of a

Decentralisation of power means the constitutional distribution of governmental authority between a central government and regional or sub-national units, so that each level exercises real, independent powers within its own sphere.

A federal state is defined precisely by this feature. In a federation, the constitution divides legislative, executive, and sometimes judicial powers between the central (federal) government and the component units (states, provinces, or regions). Neither level of government derives its powers from the other; both draw authority directly from the constitution. Examples include Nigeria, the United States, and Canada.

A unitary state is the opposite: power is concentrated in the central government, which may delegate functions to local authorities but can also withdraw them at will. A confederal state is a loose association of sovereign states that delegate limited powers to a common body; the member states retain ultimate sovereignty rather than sharing power through a constitutional division. A parliamentary state describes the relationship between the legislature and the executive (where the executive is drawn from and accountable to parliament) and says nothing about how power is distributed between levels of government.

Decentralisation of power is therefore a defining characteristic of a federal state.