The word federal in a general sense refers to the nature of an agreement between or among two or more states, nations, or other groups to merge into a union in which control of common affairs is held by a central authority created by and with the consent of the members. Each member of a federation or confederation thus formed retains jurisdiction over its own internal affairs. The word federal also characterises the group formed by such an agreement. It may also refer to the form of any government following the principle of federalism.
The word is used in a peculiar manner by some citizens of the European Union who use the term in their desire to enact certain laws over the national parliaments, (a "federal EU" would have such powers) even though certain other laws (the acquis communautaire) are readily enacted over such parliaments already. In the US, for example, each state can make its own civil and criminal law codes, while in Europe, these have already been centralized, the direct opposite of federalism.
Federal refers directly to the central government of a specific country formed by such an agreement, as:
A Federal District is a subdivision of a federal system of government, generally considered a separate entity under the direct control of the federal government. Federal District also refers to a district reserved by a country for the location of its national government, such as the United States' District of Columbia
Federal style architecture refers to a U.S. style of Georgian architecture.