TSAN

San (Ϻ) is an archaic letter of the Greek alphabet. Its shape is similar to Latin M and Greek mu (Μ), and can be described as a sigma (Σ) turned sideways. It was used as an alternative to sigma to denote the sound /s/. Unlike sigma, whose position in the alphabet is between rho and tau, san appeared between pi and koppa in alphabetic order. In addition to denoting the archaic character, the name "san" also came to be used for sigma itself.