Adolescent means a phase of life( from 12 to 18 years ) ie; transition from childhood to adulthood. This ride is not very smooth but a bumpy- ride, difficult for the girl , parents and her teachers also.
One undergoes many changes like-
Development of breast, menstruation in females, voice change in boys and many more ) , emotional, behavioral changes along with psychological, educational challenges, social ,aggression and violence, physical- health and sexual health problems. Addiction to cyberspace is also important.
Have you entered teenage years yet ? What changes you have noticed? What to expect and how to react? One should consult a doctor in case of any query.