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
Koppa (letter) the reference glyph for the Unicode code charts, along with a lowercase form with heavy curved arms and pointed angles: . Some current Unicode fonts have adopted these new shapes, while many font designers have opted for some combination of the more traditional glyphs, including the uncial and the lamedh-shaped ones. Koppa (letter) Koppa or qoppa (; as a modern numeral sign: ) is a letter that was used in early forms of the Greek alphabet, derived from Phoenician qoph . It was originally used to denote the /k/ sound, but dropped out of use as an alphabetic character in