1. How to Amend the Constitution

2. One Way (used MOST) Two-thirds (2/3) of both houses of Congress vote to propose an amendment THEN  Three- fourths (3/4) of the state legislatures approve it

3. Second Way (used once) Two-thirds (2/3) of both houses of Congress vote to propose an amendment THEN  Ratifying conventions in three-fourths (3/4) of the states approve it. This method has been used only once -- to ratify the 21st Amendment -- repealing Prohibition.

4. Third Way (never used) Two-thirds of the state legislatures ask Congress to call a national convention to propose amendments. (This method has never been used.) Three-fourths of the state legislatures approve it

5. Fourth Way (never used) Two-thirds (2/3) of the state legislatures ask Congress to call a national convention to propose amendments. (This method has never been used.) Ratifying conventions in three-fourths (3/4) of the states approve it.

6. Informally: Can be changed by: Circumstances change

7. Informally: Can be changed by: Judiciary