The letter x is not a frequently used letter, nor is it a reliable letter since the sounds assigned to it vary greatly. The most common sound representation is the /ks/ sound it makes when at the end of words such as fox and mix. X makes a /gz/ sound when it appears in the medial position, as it does in words such as exit, exam, and exact. When in the initial position, the letter x represents yet another sound. Sometimes it makes the /z/ sound, as it does in the word xylophone. Occasionally x makes the /z/ sound when in the medial position as in anxiety. X even makes the sound of its own name in words such as x-ray, and is silent at the end of Sioux. There are other sounds assigned to x: /kzh/ in luxury, and /ksh/ in anxious.