In certain languages, the final form or terminal form is a special character used to represent a letter only when it occurs at the end of a word. Some languages that use final form characters are: Arabic, Hebrew, Manchu and one letter in Greek (ς).
The lowercase Latin letter "s" had separate medial (ſ) and final (s) in the orthographies of many European languages from the medieval period to the early 19th century; it survived in the German Fraktur script until the 1940s.
Sigma (/ˈsɪɡmə/ SIG-mə; uppercase Σ, lowercase σ, lowercase in word-final position ς; Ancient Greek: σίγμα) is the eighteenth letter of the Greek alphabet. When used at the end of a letter-case word (one that does not use all caps), the final form (ς) is used. In Ὀδυσσεύς (Odysseus), for example, the two lowercase sigmas (σ) in the center of the name are distinct from the word-final sigma (ς) at the end.
In the system of Greek numerals, sigma has a value of 200. In general mathematics, uppercase Σ is used as an operator for summation. The Latin letter S derives from sigma while the Cyrillic letter Es derives from a lunate form of this letter.
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