An age generally specified by statute, at which time an individual converts or emancipates from being a minor or child to adult, and is given the full gamut of legal rights and responsibilities generally available to an adult of sound mind, such as the right to own property, to contract or to consume alcoholic beverages.
The law refers to the event as emancipation.
The age of majority is usually set by the government is a statute called "Age of Majority Act" or some similarly named law such as "emancipation of minors act", and varies from jurisdiction to jurisdiction.
As a Michigan court said in 1972:
"If a legislative body wishes, for whatever purpose, it can wave a magic wand and emancipate (a minor) to suit its convenience. Though 21 usually is the dividing line between minority and majority, the age of majority in Michigan (in 1972) is now 18. The state seemingly can be as arbitrary as it pleases in raising or lowering the barrier for all or just some purposes."
Jurisdictions do adjust the age of majority for certains decisions by an person who is otherwise a child such as reducing the age of liability for crime, or the age at which a person can vote, drive a car, marry or join the army.
For an example of a general clause, ¶1 of the relevant Alberta (Canada) statute reads simply:
"Every person attains the age of majority and ceases to be a minor on attaining the age of 18 years."
In most jurisdictions, the age of majority is between 18-21. In Scotland, Uzbekistan and Nepal it is 16.
References and Further Reading: