Most states use the term eminent domain, but some U.S. states use the term appropriation (New York) or expropriation (Louisiana) as synonyms for the exercise of eminent domain powers. The term condemnation is used to describe the formal act of exercising this power to transfer title or some lesser interest in the subject property. Where this happens, such as when an easement or a leasehold is taken, the condemner must pay just compensation, the same as in total takings.
The constitutionally required "just compensation" is usually measured by fair market value of the part taken, plus severance damages (the diminution in value of the property's remainder retained by the owner [remainder] when only a part of the subject property is taken). Where a partial taking provides economic benefits specific to the remainder, those must be deducted, typically from severance damages.
The practice of condemnation came to the American colonies with the common law. When it came time to draft the United States Constitution, differing views on eminent domain were voiced. The Fifth Amendment to the Constitution requires that the taking be for a "public use" and mandates payment of "just compensation" to the owner.
In federal law, Congress may take private property directly (without recourse to the courts) by passing an Act transferring title of the subject property directly to the government. In such cases, the property owner seeking compensation must sue the United States for compensation in the U.S. Court of Federal Claims. The legislature may also delegate the power to private entities like public utilities or railroads, and even to individuals. The U.S. Supreme Court has consistently deferred to the right of states to make their own determinations of "public use".
