What is the difference between federalism and unilateralism?

Federalism is a mixed form of government with one component being the central power and the other being regional. These two systems exist in one political system. The most distinctive feature of this government is the tight relationship and symmetry between the two. There is a division of powers, but the two systems have equal power. One of the best examples of this government is that of the United States of America.

Unilateralism in government, on the other hand, is one-sided.  This government is often a single, central power, from which all powers emanate. Any division is purely administrative, and can only use powers the central government deigns to hand down. The powers may be expanded or shrunk depending on the mood of the central power. The United Kingdom, Norway, and Sweden are considered unilateral states. 

The main difference between the two is that in countries that use federalism, both the central government and the sub-central government must consent to a change in the sub-central powers; in unilateral countries, the central government can change sub-central responsibilities indiscriminately. Both forms are valid forms of government and both have examples of functioning governments.