Own letter of the German alphabet that we don't normally have on our keyboard but that we can achieve by pressing the s with AltGr . It's this one. Equivalent to double ss after long vowel or diptongo. With uppercase, only double ss are used. I think in Switzerland where they also speak French and Italian they have eliminated it. We usually use the double ss instead as on strasse, but the Germans write strasse. They also call it scharfes s, that sharp one.