public domain, in law, legal availability for public use, free of charge, of materials, processes, devices, skills, and plans that are not protected by copyright or patent, including those on which copyright or patent has lapsed. Historically in the United States, the term has been important in reference to public land under the administration of national or local authorities.

eminent domain, the right of a government to force the owner of private property sell it if it is needed for a public use. The right is based on the doctrine that a sovereign state has dominion over all lands and buildings within its borders, which has its origins in the landholding system under feudalism. Eminent domain is implicitly enshrined in the U.S. Constitution, which in the Fifth Amendment requires that private property not be taken for public use without just compensation. The process of acquiring private property by eminent domain is known as condemnation.

Eminent domain traditionally has been used by governments to condemn land for building roads, schools, goverment buildings, and the like. The right of eminent domain may also be assigned to public and private corporations engaged in activities regarded as benefiting the public, such as the development of port facilities, the building of a canal or railroad, or the redevelopment of a blighted area. In 2005 the U.S. Supreme Court, in Kelo v. the City of New London, ruled that the Connecticut city had the right to condemn unblighted private property and transfer it to another private owner for development even if the only public benefit might be increased employment and tax revenues. Public outcry over the decision subsequently led most states to adopt legislation or constitutional amendments that limited, in varying degrees, the ability of state and local governments to use eminent domain to condemn private property for use by a private corporation. At the same time, some government officials and private developers raised concerns over how the laws and amendments would affect their ability to undertake large-scale development projects.

See also public ownership.

domain, in physics: see magnetism.

Government power to take private property for public use without the owner's consent. Constitutional provisions in most countries, including the U.S. (in the 5th Amendment to the Constitution), require the payment of just compensation to the owner. As a power peculiar to sovereign authority and coupled with a duty to pay compensation, the concept was developed by such 17th-century natural-law jurists as Hugo Grotius and Samuel Pufendorf. Seealso confiscation.

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