youngest; most junior; tiny; one (unambiguous spoken form when spelling out numbers, esp. on telephone or in military); one or ace on dice or dominoes; variant of 吆, to shout[cedict]
四
sìㄙˋ
four; 4[cedict]
洞
dòngㄉㄨㄥˋ
cave; hole; zero (unambiguous spoken form when spelling out numbers)[cedict]