Teenagers

Adolescents.. For the My Chemical Romance song, see "Teenagers (song)".

American high school students

Adolescence (Latin adolescentia, from adolescere, to grow up) is the period of psychological and social transition between childhood and adulthood (gender-specific, manhood or womanhood). In common usage in western, English language countries, "adolescent" and "teenager" may be considered synonyms (though it should be noted that the term 'teenager' is an artifact of the English counting system, not something that occurs in most languages), though the exact endpoints of each category don't always coincide depending on the definition of "adolescent" being used. Adolescence is the transitional stage of human development in which a juvenile matures into an adult. This transition involves biological (i.e. pubertal), social, and psychological changes, though the biological ones are the easiest to measure objectively.

"Adolescence" is a modern cultural and social phenomenon and therefore its end points are not easily tied to physical milestones and historically this stage of development has not existed in its current form. The time is identified with dramatic changes in the body, along with developments in a person's psychology and academic career. In the onset of adolescence, children usually complete elementary school and enter secondary education, such as middle school or high school. A person between early childhood and the teenage years is sometimes referred to as a pre-teen or tween.

The ages of adolescence vary by culture. The World Health Organization (WHO) defines adolescence as the period of life between 10 and 19 years of age.^[1] In contrast, in the United States, adolescence is generally considered to begin somewhere between ages 12 and 14, and end at 19 or 20. As distinct from the varied interpretations of who is considered an "adolescent", the word "teenager" is more easily defined: it describes a person who is thirteen to nineteen years of age.

During this period of life, most children go through the physical stages of puberty which, in recent times, has begun between the ages of nine and thirteen, while historically began much later. (See Puberty below)

Most cultures regard people as becoming adults at various ages of the teenage years. (See Social and cultural below)

Puberty

Puberty is the stage of the human lifespan in which a child develops secondary sex characteristics (for example deeper voice in boys, and development of breasts in girls) as his or her hormonal balance shifts strongly towards an adult state. This is triggered by the pituitary gland, which secretes a surge of hormones into the blood stream and begins the rapid maturation of the gonads: the girl's ovaries and the boy's testicles. Girls tend to enter puberty approximately a year earlier than boys.

The onset of puberty in girls especially appears to be related to body fat percentage. In most Western countries, the average age of menarche fell, in a secular trend, over the last century. There are numerous theories as to why this is including improved nutrition, increased caloric intake, increased artificial hormones present in meats, other preservatives and chemicals used in the modern processing of foods, and decreased melatonin levels due to the increased exposure to and prevalence of (artificial) lights such as are emitted from televisions, nightlights, and computer monitors.

Some theorists believe that analysis of data shows the age of onset of menarche to correlate to whether a girl lives with her natural father, a stepfather, or no father at all. Yet others propose a climatological connection and attribute the decreased average age of menarche in part to climate change or global warming. The debates regarding both of these theories are politically charged.

Historically this stage of development began much later, sometime between the ages of fourteen and eighteen, which allowed the child to mentally and emotionally mature more and brought them closer to the age of consent before reaching this physically and emotionally challenging developmental stage.

Preteens

The word preteen describes a child. The neologism tween has the same meaning, and isn't in general use as either a colloquial or scientific term. This word comes from the age being between that of a child and a teenager, and perhaps it has also been inspired by the first sounds of numeral twelve and the similarity to teen.

Preteens are increasingly a specifically targeted market segment by business, because they tend to maintain the preferences they develop at this age. Even mobile phones are targeted toward this group.

The definiton of when being a preteen is argued, as the term "pre" is ambiguous, however, it is generally said that being a preteen begins at age 10 and ends at age 13, at which point the child becomes teenager.

Teenagers

A teenager or teen is a person whose age is a number ending in "teen" in the English language: that is to say, someone from the age of thirteen to the age of nineteen. The word is of recent origin, only having appeared in the mid 20th century. Equivalent words in other languages may apply to a larger age bracket, including (at least some) preteens; e.g. tiener in Dutch officially from 12, colloquially from 10.

In Western culture, a distinct youth culture has developed. This culture is often distinctly different from the mainstream culture, sometimes in rebellion against it, and thus is often referred to as a subculture or counterculture.