Adolescence typically starts around age 10 or 11 at the beginning of puberty. According to the US National Library of Medicine, adolescence ends at ages 18 or 19 when adult behavior and identity has been accepted. The adolescent age range is divided into three categories known as stages of adolescence. Stages of Adolescence: Adolescence and the ... Adolescence is the transitional period when a child begins to grow into a young adult and experiences many physical, behavioral, cognitive, emotional, and social developmental changes. There are three stages of adolescence, which include early adolescence (10 to 13 years), middle adolescence (14 to 17 years), and late adolescence/young adulthood (18 to 21 years and beyond). Age is a convenient way to define adolescence, but it is only one characteristic that delineates this period of development. Age is often more appropriate for assessing and comparing biological changes (e.g. puberty), which are fairly universal, than the social transitions, which vary more with the socio-cultural environment. Adolescence, transitional phase of growth and development between childhood and adulthood. The World Health Organization defines an adolescent as any person aged 10 to 19.
