Cyrillic Capital Letter Es

It sounds like s in “sun.” The letter is called “es.” In some words its sound is softened: the middle of the tongue rises toward the roof of the mouth.

Ukrainian, Russian, Belarusian, Bulgarian, Serbian and Macedonian all use С. The letter alone tells you the text is Cyrillic, but not which language it is.

Why does Cyrillic С look like Latin C?

Its curve comes from Greek lunate sigma. That was a rounded form of the Greek letter for the s sound; Cyrillic inherited this shape rather than borrowing Latin C.

Cyrillic developed in Bulgaria around 893 for church and government writing, after Byzantine missionaries had translated Christian texts for Slavic readers. Early surviving material includes 10th–11th-century manuscripts. As Cyrillic writing spread into regional traditions, С kept its job as the s letter.