The Gutenberg Webster's Unabridged Dictionary: Section X, Y, and Z

X.

X (ks). X, the twenty-fourth letter of the English alphabet, has three sounds; a compound nonvocal sound (that of ks), as in wax; a compound vocal sound (that of gz), as in example; and, at the beginning of a word, a simple vocal sound (that of z), as in xanthic. See Guide to Pronunciation, §§ 217, 270, 271.

The form and value of X are from the Latin X, which is from the Greek...