Cedilla

The cedilla is a diacritic mark used in various languages using the Latin alphabet; it resembles a hook that is curved toward the left and that is placed below a letter, for instance: ç, ş.

Current use in Romance languages
The cedilla appared first in the Romance languages. In those tongues, c is pronounced [k] in general; but a c placed before e, i or y is pronounced with a fricative sound which is [s], [tʃ] or [θ] according to the language. The cedilla below ç indicates that the fricative sound is pronounced in another position than before e, i or y.
 * In Galician-Portuguese, French and Francoprovençal, ç before a, o, u is pronounced [s]; c before e, i is also pronounced [s]. In other positions, c is pronounced [k].
 * In Occitan and Catalan, ç before a, o, u or at word ending is pronounced [s]; c before e, i is also pronounced [s]. In other positions, c is pronounced [k].
 * In Aragonese, ç before a, o, u is pronounced [θ]; c before e, i is also pronounced [θ]. In other positions, c is pronounced [k]. It has to be noted that this use also occurred in Spanish and Asturian-Leonese but in those two latter languages, ç has been replaced progressively by z since the 16th century because z is also pronounced [θ].
 * In Friulian, ç before a, o, u or at word ending is pronounced [tʃ]; c before e, i is also pronounced [tʃ]. In other positions, c is pronounced [k].

Current use in non-Romance languages

 * In various Turkic languages (Turkish, Azeri, etc.), and in Kurdish (an Iranian language):
 * ç is pronounced [tʃ] (in contrast with c pronounced [dʒ])
 * ş is pronounced [ʃ] (in contrast with s pronounced [s]).
 * In Manx (a Celtic language), çh is pronounced [tʃ] (in contrast with ch pronounced [x]).

Diacritic marks which should not to be confused with the cedilla

 * A comma below ș and ț occurs in Romanian (a Romance language) but it is often replaced by a cedilla (ş, ţ) because of computing input problems. In an accurate typography, the comma should be prefered.
 * The ogonek resembles a hook that is curved toward the right (in contrast with the left-curved cedilla): it occurs in Polish (a Slavic language) below ą and ę and in Lithuanian (a Baltic language) below ą, ę, į, ǫ, ų. Its use has been extented to various Native American languages.

History
The first use of the cedilla appeared during the Middle Ages as a z placed below the letter ç in several Romance languages of south-west Europe (Spanish, Galician-Portuguese, Asturian-Leonese, Aragonese, Catalan and Occitan). During the 16th century, the cedilla was progressively abandoned in Spanish and in Asturian-Leonese but was extended to other Romance languages like French.

Since the 20th century, the cedilla has been adopted in other Romance languages like Friulian and Francoprovençal and in non Romance languages like Manx, Turkish, Azeri or Kurdish. Non Romance languages have extended its use on new graphemes like çh or ş.