Cedilla

A cedilla is the character ç, or just the tail that is added to the c to form it. It was used for the sound of the affricate [ts] in old Spanish.

Cedilla was later adopted for writing other languages, like French, where it represents /s/ where "c" would normally represent /k/, and Catalan. Contemporary Spanish does not use it anymore, since an orthographic reform in the 18th century.