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The age of majority is the threshold of adulthood as recognized or declared in law. It is the moment when minors cease to be considered such and assume legal control over their persons, actions, and decisions, thus terminating the control and legal responsibilities of their parents or guardian over them. Most countries set the age of majority at 18. The word majority here refers to having greater years and being of full age as opposed to minority, the state of being a minor. (Wikipedia)

full age. The age of majority, when an individual can marry, sign contracts, and so on. (YourDictionary)

A juvenile court, also known as young offender's court or children's court, is a tribunal having special authority to pass judgements for crimes that are committed by children who have not attained the age of majority. (Wikipedia)