A teenager, or teen, is someone who is 13 to 19 years old.
They can also be called "adolescents". The laws on what teenagers may do varies between countries.
The term “teenager” became widely used for people who are old enough to have their own money to spend, but are not yet adults, after the scientist Mark Abrams wrote a research paper called “The Teenage Consumer” in 1959. The paper defined this group to be people 13-25 years old (despite ages 20-25 not being within the teens anymore).
The brain is still developing into a person's early or mid-20s. A person becomes a teenager when they become 13 years old. It ends when they become 19 years old. Teenagers who are between 13 and 17 years old are considered both children and teenagers in most countries. Teenagers who are 18 and 19 years old may be considered both teenagers and adults.
The way the word is used varies. Some societies have rites of passage to mark the change from childhood to adulthood. These ceremonies may be very complicated. During puberty, rapid mental and physical development can occur. Adolescence is the name for this transition period from childhood to adulthood.
"Teenager" is mainly an English word, as many foreign languages do not include a suffix "teen" in their translations of the numbers 13 to 19. In non-English speaking countries, people between these ages may be called adolescents, youths, young adults, or just children, depending on the culture.
The law of each country may set dates when teenagers can do things. So, in the United States, alcoholic drinks are not served to young people under 21. Younger people on licenced premises (such as bars) need to carry identity cards (ID cards) to verify their age.
The life of a teenager can change every day. Constantly exposed to new ideas, social situations and people, teenagers work to develop their personalities and interests. Before their teenage years, they focused on school, play, and gaining approval from their parents.
If by "teenager" we mean adolescents, then we have to realise that children today develop faster on average mainly because of modern nutrition.[source?] No matter where the "teens" start linguistically, their sexual development starts earlier than it did a century ago. That affects many things. An example is the change from primary education to secondary education. In many countries, children go to different schools when they are 11 or 12. The change to single-sex classes is often done at the age of 11.[source?] If a country decides to educate girls and boys separately after puberty, then it may be necessary to change schools a year earlier than previously.