A change to the Constitution of the United States is called an amendment. As of 2014, there have been 27 amendments to the document.
The Constitution outlines the process of making amendments in Article V. To make an amendment to this document, two-thirds of both houses of Congress or a national convention called for by two-thirds of state legislatures must adopt the amendment, which then goes to the states. Three-fourths of state legislatures or state ratifying conventions must approve of the amendment before the Constitution changes. The first 10 amendments are better known as the Bill of Rights. The most recent amendment, the 27th Amendment, was introduced in 1789, but became enshrined in the Constitution only in 1992.