The letter ß (also known as sharp S, German: esszett or scharfes S) is a letter in the German alphabet. It is the only German letter that is not part of the basic Latin alphabet. The letter is pronounced [s] (like the "s" in "see").
The letter ß in today's form was created around 1900. It has two origins, one in Blackletter and one in Roman type. The letter came from the long s (ſ) and the normal 's' which when handwritten, over time, joined together to
The ß is only used in the German language. It appears only in the middle or at the end of German words. There is no uppercase ß. Instead of lowercase ß one can also write ss. In uppercase it is replaced with SS.
However, not every ss can be written as ß. The German language often puts two or more words together to make a longer word. If the new word has two s's together they cannot be written as ß. For example Voßstraße is two words joined together (Voß and straße). It can also be written as Vossstraße but never as Vosßtraße because "sstraße" (or ßtraße) is not a word, and the ß is in the word "Voss" (Voß).
The rules for German orthography have changed since 1996. Many common words that used to be written with ß are now written with ss. For example Fluß (river) is now spelled Fluss.