乳幼児[nyuuyouji] infants
幼い[osanai] very young
幼馴染[osananajimi] childhood friend
幼魚[yougyo] fry (young fish)
幼形進化[youkeishinka] paedomorphosis

幼子[osanago] infant
幼児[youji] infant
幼児ポルノ[youjiporuno] child pornography
幼児語[youjigo] baby talk (like choo-choo for train, etc.)
幼時[youji] childhood

悪童[akudou] bad boy
河童[kappa] kappa (mythical water-dwelling creatures)
河童巻き[kappamaki] cucumber sushi wrapped in nori (seaweed)
学童[gakudou] school child
お河童[okappa] bobbed hair (from resemblance to the mythical Kappa's hair style)

三尺の童子[sanjakunodouji] mere child
児童[jidou] children
児童画[jidouga] pictures drawn by a child
児童劇[jidougeki] juvenile play
児童心理学[jidoushinrigaku] child psychology