Well it&#x27;s used as a word in the mu koan. Might be archaic and not used in modern Chinese or Japanese, I don&#x27;t know, but for &#x27;mu&#x27; as the prefix we have (as far as I understand, which is admittedly not particularly deep) &#x27;not&#x27;. &#x27;Mu&#x27; as in &#x27;your question is based on faulty premises&#x27; is the more useful form for Westerners, I&#x27;d argue.