Topic summary
ẞ

Extracted from the Wikipedia article ß.
ß (majuscule: ẞ) is a letter of the German alphabet. In German it is called Eszett (pronounced, 'S-Z') or scharfes S (, 'sharp S'). It represents the phoneme/s/ in Standard German when following long vowels and diphthongs. In English, it is called double s, eszett, or sharp s. It is currently used only in German, and can be typographically replaced with the double-s digraph ⟨ss⟩ if the character ⟨ß⟩ is unavailable. In the 20th century, ⟨ß⟩ was replaced with ⟨ss⟩ in the spelling of Swiss Standard German (Switzerland and Liechtenstein), while remaining Standard German spelling in other varieties of the German language.