The New Student's Reference Work/X
X (ĕks), the twenty-fourth letter, is a double consonant or, rather, a superfluous sign for the compound consonants gz and ks, as in exist, wax. X, when followed by an accented syllable beginning with a vowel, or when followed by silent h and an accented vowel, is gz, as in exalt, exhort. But in a few exceptions to this rule and in other words x is ks, as in exar'chate, excellent. X at the beginning of words has the sound of z, as in xebec, and in some compounds keeps the z sound, as in meta-xylene. Final x always is ks, as in ax.