The term minor is used to refer to a person who is under the age in which one legally assumes adulthood and is legally granted rights afforded to adults in society. Depending on the jurisdiction and application, this age may vary, but is usually marked at either 12, 16, 18, 20, or 21. Specifically, the status of minor is defined by the age of majority.

In countries like Japan, Taiwan, and South Korea, a minor is a person under 20 years of age.

In New Zealand law, a minor is a person under 20 years of age, but most of the rights of adulthood are assumed at lower ages: for example, voting, entering into contracts, and having a will are all legally possible at 18.

In many countries, including Australia, Canada, India, Philippines, United Kingdom, Brazil and Croatia, a minor is presently defined as a person under the age of 18. In the United States, where the age of majority is set by the individual states, minor usually refers to someone under the age of 18, but can be used in certain areas (such as gambling and the consuming of alcohol) to define someone under the age of 21.

In the criminal justice system in some places, minor is not entirely synonymous, as a minor may be tried for a crime (and punished) as a juvenile or an adult (usually only for extremely serious crimes such as murder).