An amendment to a constitution is a change in the fundamental law of a country. A constitutional amendment requires a special procedure for its passage, which is usually more stringent than the process required for passing ordinary legislation. This special procedure may involve a supermajority in the legislature or direct approval by the electorate in a referendum. In some countries, there are even multiple different special procedures for passing an amendment to the constitution.
Most countries also include an entrenched clause in their constitutions that prohibit the passage of certain types of amendments, unless the state in question is at war or in a state of emergency. These clauses are generally intended to protect characteristics of a country that are considered sacrosanct, such as a democratic form of government or the protection of human rights.
A constitutional amendment can only be ratified by the legislatures of three-fourths of the States. Once the amendment has been ratified by the necessary number of States, it becomes an official part of the constitution and can be cited in legal cases.
In the United States, a proposed constitutional amendment must be approved by the Congress, and then the President of the United States must sign it into effect. Once the amendment has been ratified, it must be authenticated by the National Archives and Records Administration (NARA). The Archivist then drafts a proclamation that certifies that the amendment has been officially ratified by the required number of States and contains a list of those States. The proclamation is then published in the Federal Register and U.S. Statutes at Large, and serves as official notice to the Congress and the Nation that the amendment has been ratified.