Whats this letter ς

Answer 1

The letter ς is called "sigma" and is the lowercase form of the Greek letter Σ (sigma). In modern Greek, it represents the "s" sound, while the uppercase Σ represents the same sound at the beginning of a word or in all-caps text. However, in ancient Greek, the letter ς (sigma) was only used at the end of words, while the letter σ (sigma) was used elsewhere