Stigma (letter) Stigma (letter) Stigma (ϛ) is a ligature of the Greek letters sigma (Σ) and tau (Τ), which was used in writing Greek between the Middle Ages and the 19th century. It is also used as a numeral symbol for the number 6. In this unrelated function, it is a continuation of the old letter digamma (originally Ϝ, cursive form ), which had served as a numeral since antiquity and was conflated with the σ-τ ligature in the minuscule handwriting of the Middle Ages. The στ ligature (, ) was one of many ligature forms that came into widespread use as
Greek alphabet the abjads used in Semitic languages, which have letters only for consonants. Greek initially took over all of the 22 letters of Phoenician. Five were reassigned to denote vowel sounds: the glide consonants ("yodh") and ("waw") were used for [i] (Ι, "iota") and [u] (Υ, "upsilon") respectively; the glottal stop consonant ("|aleph") was used for [a] (Α, "alpha"); the pharyngeal ("ʿayin") was turned into [o] (Ο, "omicron"); and the letter for ("he") was turned into [e] (Ε, "epsilon"). A doublet of waw was also borrowed as a consonant for [w] (Ϝ, digamma). In addition, the Phoenician letter for the emphatic