Answer:
It is called a Constitutional Amendment to those additional articles that are added to the text of the Constitution of the United States, guaranteeing civil rights of American citizens. Thus, the amendments are modifications to the original text of the Constitution.
The procedure by which the Constitution can be amended is described by Article Five of the same. Basically, it states that any amendment, whether proposed by 2/3 of the entire Congress or by 2/3 of the states, must be ratified by 3/4 of the state legislatures to become part of the Constitution.