Short Answer 
The letter **q** is unique in the English alphabet as it never appears at the end of a word and is always followed by **u**. Examples illustrate this rule, such as in the words queue, quit, quail, and quest.
Step 1: Identify the Unique Letter
The letter q is the only letter in the English alphabet that has a specific characteristic. It is never found at the end of any English word. This uniqueness is crucial for understanding the structure of English words.
Step 2: Understand Its Relationship with Another Letter
In every instance where q appears in a word, it is always followed by the letter u. This phonetic pairing is an essential rule in English spelling. For example, in the words queue, queen, and quit, the presence of q necessitates that it is immediately followed by u.
Step 3: Recognize Examples of This Rule
To solidify your understanding, consider these examples where q can be found:
- queue
- quit
- quail
- quest
In all these cases, you can see that q is never at the end, reinforcing its unique role in the English language.