pu ‧ ber ‧ ty /ˈpjuːbəti $ -ər-/ BrE AmE noun [uncountable]
[ Date: 1300-1400 ; Language: Latin ; Origin: pubertas , from puber 'pubescent' ]
the stage of physical development during which you change from a child to an adult and are able to have children:
Fourteen is a fairly normal age for a girl to reach puberty.