living organism that has reached sexual maturity

An adult may mean different things. In law and social norms, an adult is a human who has reached the age of majority. The age of majority is the age at which an individual will be legally considered an adult. That age varies: in most countries, an adult is a person who is 18 years old or older. Once someone is adult, they no longer have to take directions from a parent or guardian but can make decisions for themselves, and be held responsible for their own actions. Legal penalties for crimes are different before and after the age of majority.

There are many factors that constitute being an adult. An adult is much more than turning the age of 18. The definition in the dictionary states an adult means being completely grown: fully developed and mature. There is much more that defines an adult. In the United States an adult is considered to be someone who takes responsibility for themselves and their actions. An adult has stability in their life and is able to take care of themselves physically, mentally, financially and emotionally. In other countries and cultures their definition of an adult differs. Adults are unique in many ways. Every person is an entity having their own identity, thought process, and way they see things.

In contrast, a person who has not yet reached the age of majority is a minor.

There are additional laws that decide from what age a person is allowed to do something; for example, vote, drink alcohol, and have sexual intercourse. For example, in the United States, a person becomes an adult on their 18th birthday, but they cannot buy alcoholic beverages until they turn 21. To verify their age, a young person must have an I.D. card for inspection by the bartender.

There are also some cultures that says a person is an adult from an age of 13 years on, for example see Bar Mitzi, which usually corresponds to puberty.[1]

In biology, an animal is an adult when they are sexually mature. This means that they are able to sexually reproduce.[2]



  1. Rew, Martin. 2011. Religion and development I: Anthropology, Islam, transnationalism and emerging analyses of violence against women. Progress in Development Studies 11.1: 69-76.
  2. Abercrombie et al. 1951. The dictionary of biology. London, Penguin, p512 to 514 gives a full account.