Mu or the gentle art of unasking the question

Mu (Japanese/Korean), Wu (Chinese)and Vo (Vietnamese) is a word which can be roughly translated as "none" or "without". While typically used as a prefix to imply the absence of something, it is more famously used as a response to certain koans and other questions in Zen Buddhism, intending to indicate that the question itself was wrong.

The Mu koan is as follows: A monk asked Zhaozhou, a Chinese Zen master, "Has a dog Buddha-nature or not?", Zhaozhou answered "Wu".
"Your question cannot be answered because it depends on incorrect assumptions".