cedilla

noun

1. a mark (¸) placed under a consonant letter, as under c in French, in Portuguese, and formerly in Spanish, to indicate that it is pronounced (s), under c and s in Turkish to indicate that they are pronounced, respectively, (ch) and (sh), or under t and s in Romanian to indicate that they are pronounced, respectively, (ts) and (sh).
2. this mark used as a diacritic of arbitrary value in transliteration of words from non-Roman into Roman alphabetic characters.

noun

1. a character ( ¸ ) placed underneath a c before a, o, or u, esp in French, Portuguese, or Catalan, denoting that it is to be pronounced (s), not (k). The same character is used in the scripts of other languages, as in Turkish under s

n.

c.1600, from Spanish cedilla, zedilla, literally “little z,” from a Latin-like diminutive of Greek zeta “the letter ‘z’.” The mark (formerly also used in Spanish) was derived from that letter and indicates a “soft” sound in letters in positions where normally they have a “hard” sound. See zed.