A "constitutional amendment" is a formal change or addition to a country's constitution, requiring a specific procedure for adoption. In the U.S., for instance, amendments can be proposed by a two-thirds majority in both the House of Representatives and the Senate or by a national convention called by two-thirds of state legislatures. To be ratified, proposed amendments must receive approval from three-fourths of the state legislatures or state conventions. Constitutional amendments are significant as they reflect societal changes, address evolving values, and enhance the document's relevance over time, shaping the country's legal framework and guiding principles.