Mu (Japanese/Korean), and Wu (Chinese traditional: 無, simplified: 无pinyin: wúJyutping: mou2), is a word which has been roughly translated as "no", "none", "null", "without", and "no meaning". While used in Japanese and Chinese mainly as a prefix to indicate the absence of something (e.g., 無線/无线 musen or wúxiàn for "wireless"), in English it is better known as a response to certain koans and other questions in ZenBuddhism, intending to indicate that the question itself was meaningless.
The best-known mu koan is as follows: A monk asked Zhaozhou Congshen, a Chinese Zen master (known as Jōshū in Japanese), "Has a dog Buddha-nature or not?" Zhaozhou answered, "Wú" (in Japanese, Mu).[page needed]
Some earlier Buddhist thinkers maintained that animals did have Buddha nature, others believed that they did not. Zhaozhou's answer, which literally means that dogs do not have Buddha nature, has been interpreted to mean that such categorical thinking is a delusion, that yes and no are both right and wrong. This koan is traditionally used by Rinzai school to initiate students into Zen study.
For example, it's stated over and over again that computer circuits exhibit only two states, a voltage for "one" and a voltage for "zero." That's silly! Any computer-electronics technician knows otherwise. Try to find a voltage representing one or zero when the power is off! The circuits are in a mu state.
According to the Jargon File, a collection of hacker jargon and culture, mu is considered by Discordians to be the correct answer to the classic logical fallacy of the loaded question, "Have you stopped beating your wife?" Assuming that you have no wife or you have never beaten your wife, the answer "yes" is wrong because it implies that you used to beat your wife and then stopped, but "no" is worse because it suggests that you have one and are still beating her. As a result, some Discordians proposed "mu" as the correct answer, which to them means, "Your question cannot be answered because it depends on incorrect assumptions."
The idea, more often called "Null", is often an essential component of ternary logic systems, which, unlike classical bivalent systems (e.g. Boolean logic), often use the third value to represent the idea of a meaningless question. Some implementations of SQL, notable Oracle's, implement a full ternary logic set, and many expressions evaluate to Null instead of True or False. The initial value of an unassigned variable, for example, is Null.