Age at which an individual has the legal capability of being responsible for his or her actions (e.g., enter into a contract or vote in a national election). In most states the age of majority is 21 years, but in some it is 18 because of enactment in 1972 of the 26th Amendment of the U.S. Constitution, which allowed 18-year-olds to vote in federal elections. Also known as legal majority or emancipated minor.