Mu-Law is the standard codec (compression/decompression) algorithm for pulse code modulation (PCM) from the CCITT (Consultative Committee for International Telephone and Telegraph). A companding (compression/expanding) method, mu-Law makes it possible to improve the signal-to-noise ratio without requiring the addition of more data. Mu-Law, as a term, was derived from µ-Law, because the Greek letter µ is pronounced myoo. The term is sometimes seen as u-Law, although the pronunciation remains the same.
Mu-Law is used in the United States and Japan. The other type of codec algorithm, A-Law, is the standard used in Europe and elsewhere.