ks
fifteenth (later fourteenth) letter of most of the Eastern Greek alphabets, including the Ionic (later general Gr.) alphabet ; not used in Western Greek alphabets or in the native Attic alphabet ; in form and serial position (IG 14.2420) it corresponds to the Semitic samech (a form of s), but has acquired the new value ks ; as numeral ξʹ = 60, but ͵ξ = 60,000.