Ξ ξ,
ξεῖ (which see), τό, indeclinable, 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)] Refs] it corresponds to the Semitic samech (a form of s), but has acquired the new value ks; as numeral ξ᾽ = 60, but ξ᾽ = 60,000.