The Constitution can be changed through both formal and informal processes. A formal change is called an amendment, or addition. To amend the Constitution, it has to be voted on by both houses of Congress by a two-thirds majority. So, be it formally or informally, the U.S. Constitution is made to be changed.
Formally:
There are a couple ways that the U.S. Constitution could be formally amended. First Congress could adopt a proposed amendment (2/3 majority vote in both House of Representatives and Senate) and then send that proposed amendment to the state legislatures to be adopted - 3/4 majority required.
Informally:
States or the federal government can propose a new amendment to the Constitution either through state conventions or a two-thirds majority vote in both the House and the Senate. To ratify an amendment to the Constitution, three-fourths of state legislatures or three-fourths of special state conventions must approve it.
