in terms of growth rate the following five age periods were identified in the predefinitive stage of postnatal ontogenesis : childhood -- from birth to 9 months of age , adolescence -- from 9 months to 3 years , accelerated growth or pubescence -- from 3 to 4.5 years , growth completion -- from 4.5 to 7-8 years , and physiological maturity ( definitive stage ) -- over 8 years of age .
C0231335
childhood
C0001578
adolescence