An adult is a person who is grown up completely, or is not a child anymore. It is the phase after being a teenager. Once someone reaches adulthood, that person typically no longer has to take directions from a parent or guardian, but rather can make decisions for themselves.
In most countries, someone is legally considered an adult when he or she is older than a certain age. This is called the Age of majority. In most countries, this age is 18 years. However, it varies from ages as low as 16 to as high as 21. There are many additional laws that determine from what age a person is allowed to do something; for example, vote and drink alcohol.
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