Mu

Part of speech: noun

Definitions

1. The twelfth letter of the Greek alphabet, written as a lowercase letter resembling a small u with a descending tail ; a Zen Buddhist reply meaning neither yes nor no, given to an unanswerable question
2. A letter in the Greek alphabet, shaped like a small u with a hanging stroke ; a Zen term used to decline a question that cannot be answered with yes or no
3. The Greek letter numbered twelve, often used as a symbol in science and mathematics ; a Zen Buddhist answer signaling that a question has no simple yes or no reply

Etymology: The Greek letter mu began its life as a picture of water. Its name comes from the Phoenician "mem," meaning "water," and the letter's shape was originally a wavy line, which the Greeks adopted and kept as their twelfth letter, μ. English speakers mostly meet it in science, where it stands for the prefix micro- in units such as micrometre, and as a symbol for the mean in statistics. The same spelling also names a common English word of a completely different origin: "mu" as a word for "nothing" or "neither yes nor no" comes from the Japanese 無. In Zen Buddhist contexts it is a famous answer to questions that cannot be resolved with a simple yes or no, and it entered English through that Japanese and Buddhist usage. Mu is also a unit of land area in Chinese, written 畝 or 亩, a term used for a field measure. Three unrelated words thus share one spelling, one from a Phoenician picture of water, one from a Japanese word for nothing, and one from a Chinese measure of land.