Formal method of amending the United States Constitution:
Article V creates a two-stage process for amending the Constitution: proposal and ratification.
An amendment can be proposed by two-thirds of both houses of Congress or...
By two-thirds of state legislatures requesting Congress to call a national convention to propose amendments.
An amendment can be ratified by a favorable vote in three-fourths of all state legislatures or by such a vote in specially called ratifying conventions called in three-fourths of the states.
Informal method of amending the United States Constitution:
By judicial interpretation (in Marbury v. Madison-1803- the Supreme Court declared that the federal courts had the power to nullify actions of the national government if found to be in conflict with the Constitution.
Social, cultural and legal change.