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 Braille ά, Ά, αί. It's not used for diaeresis; ϊ is just . Digits are the same as in English Braille. Arithmetical symbols are: International letter assignments differ somewhat from those above. In Modern Greek Braille, for example, the letter omega (ω) is written the same as Latin "j", whereas in English or French braille texts it is written as a "w", which it resembles in print. Similarly, Modern Greek upsilon is written as Latin "y", but in international Greek it's written as "u", and the letter eta is inverted. This alphabet is used, for example, in mathematical notation in an