San (letter) San (letter) San (Ϻ) was an archaic letter of the Greek alphabet. Its shape was similar to modern M, or ϡ, or to a modern Greek Sigma (Σ) turned sideways, and it was used as an alternative to Sigma to denote the sound . Unlike Sigma, whose position in the alphabet is between Rho and Tau, San appeared between Pi and Qoppa in alphabetic order. In addition to denoting this separate archaic character, the name "San" was also used as an alternative name to denote the standard letter Sigma. The existence of the two competing letters Sigma and San is
History of the alphabet All of the names of the letters of the Phoenician alphabet started with consonants, and these consonants were what the letters represented, something called the acrophonic principle. However, several Phoenician consonants were absent in Greek, and thus several letter names came to be pronounced with initial vowels. Since the start of the name of a letter was expected to be the sound of the letter (the acrophonic principle), in Greek these letters came to be used for vowels. For example, the Greeks had no glottal stop or voiced pharyngeal sounds, so the Phoenician letters "’alep" and "`ayin" became Greek "alpha"