1. INFORMAL AND FORMAL AMENDING

2. INFORMAL AMENDING
Sometimes the Constitution can be changed and added to without a nationwide vote

3. Congressional Legislation
Congress passes laws, under its given powers.
Such as the Commerce Clause
Regulation of interstate and foreign commerce.

4. Presidential Actions Introduces Bills
Sends troops to war, without declaring war
Executive agreements- with other heads of state, which are legally binding

5. Interpretation of the Constitution to match the times
Judicial Review
Interpretation of the Constitution to match the times
Technology
Transportation etc.

6. Political Parties
Not mentioned in the Constitution but profoundly effect the outcome and interpretation of it.

7. Custom and Usage
Custom:
Cabinet members and approval
Usage:
Vice president inherits in death

8. FORMAL AMENDING Proposing Amendments
2/3 vote in the Senate and the House
All 27 proposed this way
2/3 of state legislatures request a national convention, with a simple majority.
Never used

9. Ratifying Amendments 3/4 of State Legislatures can vote in favor
Traditional ratification method 26, amendments ratified this way
3/4 of states can call special conventions to ratify.