Final answer:
Adolescence is the period of transition between childhood and adulthood, usually starting with puberty. It involves physical, cognitive, and psychosocial changes.
Step-by-step explanation:
Adolescence is the period of transition between childhood and adulthood. It is generally considered to start with puberty, during which sexual maturation occurs and adolescents go through a spurt in growth. In many children, however, puberty actually begins during the stage called pre-adolescence, which covers the ages 11 to 12 years. Besides the physical changes of puberty, adolescence is also a time of significant cognitive and psychosocial changes. Many of these changes continue through the end of adolescence after most of the physical changes of puberty have already taken place.