An adult is generally considered to be someone who has reached the age of majority, which is 18 years old in most countries, including Australia, granting full legal rights and responsibilities, though the definition varies by culture, country, and specific laws (like drinking age or voting age). While 18 is the typical legal benchmark for independence, the transition to adulthood involves gradual legal and social changes, with some privileges (like voting) at 18, but others (like drinking in the US) at 21.
In Australia, you're considered to be an adult when you turn 18 years old. But for certain things, the legal age can be younger. The information in this article is general, and laws differ from state to state.
The adult age, or age of majority, is legally set at 18 in most countries, including the US and Australia, marking when someone gains full legal rights and responsibilities, though specific ages for things like driving, drinking, or voting can vary by jurisdiction. Biologically, physical maturity happens earlier, while culturally, "adulthood" involves increased responsibility, often shifting from parental to personal control, typically seen in the late teens or early twenties.
Age of criminal responsibility
If they were under 18 when the alleged offence occurred and have not yet turned 21, they are considered a 'child' under the law. In this section of the website, and in the courts, a 'child' charged with a criminal offence is referred to as a 'young person'.
A person between 20 and 29 is called a vicenarian. A person between 30 and 39 is called a tricenarian. A person between 40 and 49 is called a quadragenarian. A person between 50 and 59 is called a quinquagenarian. A person between 60 and 69 is called a sexagenarian.
Around 70% of those surveyed hit their happiness peak then, compared to 6% in college years and 16% in childhood. Over half of us believe life is more fun in our early 30s. It's a stage that heralds in more optimism and less stress than before (probably because we've learnt not to care so much).
Gen Y: Gen Y, or Millennials, were born between 1981 and 1994/6. They are currently between 29 and 44 years old (around 74 million in the U.S.)
In Australia, the age of consent is between 16 and 17 years, depending on the state. The primary aim of these laws is to protect minors from sexual abuse and exploitation. This is because minors don't have the maturity to consent to various sexual activities, thus needing protection.
In the United States, a minor is any individual under the specified “age of majority” for their state or territory., All states define an age of majority, which is usually set at 18, but states like Indiana and Mississippi set it at 21, while in Alabama, Colorado, Maryland, or Nebraska, the age of majority is 19.
18 Means Reaching the Age of Majority
In most states, 18 years old is considered the age of majority when your teen is considered an adult.
Some inclusive definitions extend the range into the early to mid 40s, while others end earlier. The young adult phase is typically defined as lasting from around the age of 18 to 25. The brain also finishes its development during this period, transitioning into full adulthood.
Most countries set the age of majority at 18, but some jurisdictions have a higher age and others lower. The word majority here refers to having greater years and being of full age as opposed to minority, the state of being a minor.
The study compared the brains of 3,802 people between ages 0 and 90 and found that there are five brain phases: childhood from birth to age 9, adolescence from 9 to 32, adulthood from 32 to 66, early aging from 66 to 83 and late aging from 83 onwards.
So the 21st birthday is a significant turning point for a young adult as they're now able to partake in more adult activities, legally. Given Australia has inherited much from American culture, it's no surprise we've adopted this as well. That aside, Australia's legal drinking age wasn't always 18 for all states.
A Guide through the 6 Domains of Adulthood
Most, if not all, young adults need assistance as they enter adulthood. Reaching the age of majority, typically at 18 (*states or territories may vary), marks an important transition into adulthood.
Parents, as a general rule, have full parental responsibility for any of their children who are under 18 years. The law does however see that parental responsibility over you may reduce as you get closer to 18 and become mature enough to make your own decisions. There is no law that says what age you can leave home.
17-year-olds will seem more emotionally mature as they: Move toward a more adult sense of themselves and their purpose. Cope better with new problems and different situations than they did at younger ages (called fluid intelligence and emotional regulation).
WHO defines 'Adolescents' as individuals in the 10-19 years age group and 'Youth' as the 15-24 year age group. While 'Young People' covers the age range 10-24 years.
What Can You Do at 18 Legally?
Teenager is a numeric term for a person from the ages of 13 to 19 years.
Over 18 you are no longer the responsibility of your parents. They can remove you from the home. And many do. We have lots of teens homeless or in insecure housing situations because of this.
Whilst boomers and millennials may use the 😂 emoji, this has long since been deemed 'uncool' (or 'cheugy') by Gen Z. Instead, this has been replaced by the skull (💀) or the crying emoji (😭), dramatising the idea of 'dying with laughter'.
While other cohorts (e.g., Baby Boomers, Generation X, Millennials, Generation Z) are defined by age brackets, Gen C is defined by its members' digital-first lifestyle and mindset. So whether someone is 10 or 82 years old, they can still be a part of Gen C.
Zoomers (Generation Z) are people born between 1997 and 2012, making them approximately 13 to 28 years old in 2025, a digitally native cohort that followed Millennials and precedes Generation Alpha, known for growing up with the internet and smartphones.