Final answer:
An amendment changes or alters a main motion by modifying the U.S. Constitution. The process to propose and ratify amendments requires approval from both the House of Representatives and the Senate, or from a majority of the states. Amending the Constitution is a deliberate and difficult process.
Step-by-step explanation:
An amendment changes or alters a main motion by modifying the U.S. Constitution. In the U.S., amendments to the Constitution can be proposed by two-thirds approval in both the House of Representatives and the Senate, or by two-thirds of the states calling for a convention. Once proposed, amendments must be ratified by three-fourths of the state legislatures. This process ensures that amending the Constitution is a deliberate and difficult process.