Many parents claim that turning 18 does not make their children adults and treat them like troubled adolescents. Especially, when the wanna-be adults depend on their parents financial support, continue their education and live in the family house. But in my opinion, adulthood is a state of mind, not determined by one's age in years and depends on one's experience.  

Becoming an adult is the process of forming a character and mind, and adulthood, without being proved, is only the birth certificate. Following the law of the age of majority or the age of which one is permitted certain licences can be misleading and puzzling. In the UK, and in the most countries, a person becomes an adult with the right to vote, which is given when one turns 18. But there are some other ages of license, which entitle a young person to do what an adult can, so at the age of: 12 one has to buy an adult travel ticket, 16 one reaches the age of consent and may drop out the education, 17 one can join the Army and get a driving licence, 18 - watch X-rated movies and marry, 21 - buy alcohol and cigarettes. 

Coming of age, even for the law-makers, seems to be rather a process than crossing the invisible line between adolescence and adulthood. And yet, in our modern times, there are two tendencies among young people: teenage parenthood or thirty-something singlehood, both scrutinized by the media and authorities as being not responsible; therefore, indicating the lack of adulthood. Additionally, the older we are, the less prone to accept a young person as a fully adult. Similarly, young people's perception of adulthood depends on some achievements: education, financial independence, starting a family, having a child and fully supporting them. 

It is by far easier to identify adulthood in the animal kingdom. For example, a female leopard is forced to abandon her mother when she reaches puberty; nonetheless, she has to prove her independence by her first big game kill, indicating her ability to survive and to feed her future cubs. It is not a point in time, but gaining some vital experience in life. In human society, on the other hand, the perception of adulthood changes throughout the history and culture. First of all, the notion of adulthood referred only to the male members of society and could be reached as early as 14-16 years of age in some tribes and in the Middle Ages; however, in the Roman Empire a man was entitled to stand for a place in the Senate when he reached the age of 30, and therefore was accepted as an adult person.

Summing up, I think that adulthood is the ability to be responsible for himself or herself and for the society. Moreover, it implies that a person has to have some positive and negative experience, which strengthened her or his character, gave an insight into the complexity of human society and her or his own strong and weak points. One may turn 30 and still be an adolescent, whereas another person, only 16 years old be already recognized as an adult. Being an adult means to be a reliable part of the society, and this society's recognition gives a person the rights to be an adult.