Ancient/Classical History/the character "C"
I visited some ancient Greek carvings and mosaics that used this character in certain words (that is, not as a numeral). What does it represent?
the ancient Greek letter “C”, used in some carvings and mosaics as well as in some editions of classical Greek texts, is the so-called “lunate sigma”, which is an alternate form of the sigma, the 18th letter of the Greek alphabet usually written as Σ in its upper case.
Such a form of the sigma, equivalent to ”S” in Latin alphabet, is known as "lunate sigma" because its crescent shape resembles a half moon and the Latin word for moon is just “luna”.
In short, the lunate sigma “C” (upper case) or “c” (lower case) corresponds to the capital letter Σ whose small letter is “σ “ that appears in any position of a Greek word, except for the final letter, where it becomes “ς “ used only at the end of Greek words.
Lastly, I have to point out that the lunate sigma began to be used in handwritten Greek during the Hellenistic period (4th and 3rd centuries BC), when the epigraphic form of Σ was simplified into a C-like shape.
This "C" became the universal standard form of Sigma during late antiquity and the Middle Ages and it is still widely used in decorative typefaces in Greece, especially in religious and church contexts as well as in some modern print editions of classical Greek texts, as I’ve already said.
For mosaics, see for example the Mosaic of Christ Pantocrator from Hagia Sophia, Istanbul, where the acronym IC represents the Greek characters Iota (Ι) and Sigma (Σ , C), i.e.the first and last letters of Jesus (Ἰησοῦς), while the letters XC represent Chi (Χ) and Sigma (Σ, C), i.e. the first and last letters of Christ (Χριστός ):
Hope all is clear enough.