At what age is an individual legally defined as an adult?

An individual is legally defined as an adult at the age of 18 years in most jurisdictions, including the United States. This age marks the transition from childhood to adulthood, granting individuals the full legal rights and responsibilities that come with being an adult. At this age, a person can enter into contracts, vote in elections, and be tried as an adult in the criminal justice system. The establishment of 18 years as the age of majority is also significant in various legal contexts, such as the ability to serve in the military, obtain a driver's license independently, and manage personal finances.

While some activities may have different legal ages (for instance, 21 years for alcohol consumption), 18 is recognized as the standard age when individuals are considered fully responsible for their actions under the law. This understanding is crucial for various legal, social, and civic responsibilities that begin when a person reaches this age.