Unitary states stand in contrast with federations, also known as federal states. In federations, the sub-national governments share powers with the central government as equal actors through a written constitution, to which the consent of both is required to make amendments. This means that the sub-national units have a right of existence and powers that cannot be unilaterally changed by the central government.
^Ghai, Yash; Regan, Anthony J. (September 2006). "Unitary state, devolution, autonomy, secession: State building and nation building in Bougainville, Papua New Guinea". The Round Table. 95 (386): 589–608. doi:10.1080/00358530600931178. ISSN0035-8533.
^Devolution within a unitary state, like federalism may be symmetrical, with all sub-national units having the same powers and status, or asymmetric, with sub-national units varying in their powers and status.