noun

a young human being below the age of puberty or below the legal age of majority.

she’d been playing tennis since she was a child

youngster,young one,little one,boy,girl,baby,newborn,infant,toddler,schoolboy,schoolgirl,adolescent,teenager,youth,young man,young woman,young lady,young person,young adult,juvenile,minor,junior,stripling,fledgling,whippersnapper,son,daughter,son and heir,scion,descendant,offspring,progeny,issue,neonate,bairn,wean,laddie,lassie,pickney,kid,kiddie,kiddiewink,nipper,tot,tiny,tiny tot,shaver,young ‘un,lad,lass,teen,teenybopper,sprog,rug rat,ankle-biter,babe,babe in arms,hobbledehoy,brat,chit,urchin,guttersnipe