Ξ ξ

Ξ ξ, [full] ξεῖ (q.v.), τό, indecl., 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 (IG14.2420) it corresponds to the Semitic

A samech (a form of s), but has acquired the new value ks ; as numeral ξ' = 60, but [num] ξ' = 60,000.