Physical growth is an increase in size. Development is growth in function and capability. Both processes highly depend on genetic, nutritional, and environmental factors.
As children develop physiologically and emotionally, it is useful to define certain age-based groups. The following terminology is used:
Neonate (newborn): Birth to 1 month
Infant: 1 month to 1 year
Young child: 1 year through 4 years
Older child: 5 years through 10 years
Adolescent: 11 years through 17 to 19 years