THE LETTER X - the twenty-fourth letter of the English alphabet. Its position and form are derived from the Latin alphabet, which received them from the Western Greek alphabet. The alphabet of the Western Greeks differed from the Ionic, which is the Greek alphabet now in general use, by the shape and position of X and of some other consonants. The Ionic alphabet placed x immediately after N and, in the oldest records, in the form ^, from which the ordinary Greek capital E was developed. The position and shape of this symbol show clearly that it was taken from the Semitic Samekh, which on the Moabite stone appears as ^=. Why the Greeks attached this value to the symbol is not clear; in Semitic the symbol indicates the ordinary s. Still less clear is the origin of the form X> which in the Ionic alphabet stands for x (* followed by a breath). In a very ancient alphabet on a small vase found in 1882 at Formello near the ancient Veii in Etruria, a symbol appears after N consisting of three horizontal and three vertical lines, EB- From this it has been suggested that both forms of the Greek * are derived, H by removing the vertical lines, X in its earliest 'form -f" by removing the four marginal lines. The Ionic symbol, however, corresponds closely to the earliest Phoenician, so that this theory is not very plausible for E, and there are various other possibilities for the development of X (see ALPHABET). This symbol appears in the very early Latin inscriptions found in the Roman Forum in 1899 as 7^. In its usual value as ks it is superfluous. In the Ionic alphabet it was useful, because there it represented a single sound, which before the invention of the symbol had to be represented by kh. In the alphabet in use officially at Athens before 403 B.C. x was written by x^ (khs). In English there is an interesting variation of pronunciation in many words according to the position of the accent: if the accent precedes, x is pronounced ks; if it follows, x is pronounced gz: compare exit (eksit) with exdct (egzact).
The symbol X was used both by the Romans and the Etruscans for the numeral 10. Which borrowed from the other is uncertain, but the Etruscans did not use X as part of their alphabet. X with a horizontal line over it was used for 10,000, and when a line on each side was added, |X|, for a million. (P. Gi.)
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)