"X Stands for Nothing"
To avoid the issue of the letter x all together, some authors have simply noted that “X stands for nothing,” or some version of said expression. This approach neither enforces the auditory-visual connection typical of alphabet books nor does it expand the vocabulary of the reader.
In some instances, the authors also take this opportunity to lump ‘x,’ ‘y,’ and ‘z’ together in one entry, avoiding assigning words to all three of these letters.