WHO defines adolescent age between –
First see the difference between adolescence and puberty.

Adolescence

Adolescence is defined as the period from the onset of puberty to the termination of physical growth and attainment of final adult hight, i.e. adolescence is considered as a period of transition from childhood to adulthood. Adolescence is usually the period 10 to 20 yr.

Puberty

Puberty is the biological process in which a child become adult, i.e. biological process which occurs during transition from childhood to adulthood. Changes include appearance of secondary sex characteristics and development of reproductive capacity.
10–19 years
10–14 years
10–25 years
9–14 years