Wyvern (from Lat. vipera), a fictitious monster allied to the dragon and the griffin, and frequently occurring in heraldry. It resembles a dragon, but has only two legs and feet, which are like those of the eagle.

X

the last letter in the pre-Ciceronian Roman alphabet, and the twenty-fourth in our own, is descended through the Greek Xi from Samekh, the fifteenth Semitic letter, whose Egyptian parentage is explained in the article ALPHABET (Vol. I. p. 187). The oldest form of xi was $\backslash Xi$, which is almost identical in form with the Phoenician letter. In the eastern Greek alphabet the vertical stroke disappeared and the form became $\backslash Sigma$, which has the value of x in Greek. In the Chalcidian and Western alphabets the upper and lower crossbars disappeared, leaving the sign +, which afterwards became x, to represent the sound of x. In the eastern Greek alphabet the unrelated sign $\backslash chi$, derived from another source, represented the sound ch. In the original Italic alphabet the letter must have existed, as is proved by its occupying, like xi, the fifteenth place, after n, in three ancient abecedaria recently discovered in Italy; but its position at the end of the Latin alphabet, ultima nostrarum, as Quintilian calls it, proves that it must have been disused and then afterwards re-adopted. It is found in an inscription written in 186 B.C., and in an undated inscription which may be some thirty years earlier. In modern English x has the value of ks, which it had in Anglo-Saxon; except at the beginning of a word, where it is pronounced like z. In Italian x has been replaced by ss, as in massimo for maximus. In French ss sometimes replaces x, as in cuisse and laisser, from coxa and laxare, while us may become ux, as in yeux, eux, deux, and époux. In Spanish x had the power of the German ch, but the Spanish Academy has decreed its replacement by j; Mexico, Xalapa, and Don Quixote being now spelt Mejico, Jalapa, and Don Quijote. As a numeral, X stands for ten (see NUMERALS); X as an abbreviation represents the word Christ (see CROSS)—hence Xian, Xmas; x in Algebra is the first of the unknown quantities; and the use of X, XX, and XXX on barrels of stout is a well-known way of indicating the quality.