Amendment (U.S. Constitution)

Spell out through Ninth Amendment. An enacted and ratified amendment is capitalized when its number is used:

            the Fifth Amendment

            the 10th Amendment

            the 18th Amendment

Lowercase informal titles unless they include words that are capitalized in their own right:

            income tax amendment

            the Prohibition amendment

A proposed constitutional amendment should be lowercase:

            equal rights amendment (ERA)

            the Bricker amendment