It commonly represents the voiceless alveolar fricative /s/, like the pronunciation of ⟨s⟩ in "sand".

The Cyrillic letter Es is derived from a variant of the Greek letter Sigma known as lunate sigma (Ϲ ϲ), in use in the Greek-speaking world in early medieval times.

“Es” (Cyrillic: С) is related to the Latin letter “C” (C c), visuo-phono-semantically due to being a homoglyph and having similar roots, which C is a descendant of the Greek letter Gamma (Γ γ), and therefore С is related to the Latin C and Latin G. While the Cyrillic “С” represents the /s/ sound, many languages apply the value of /s/ to the Latin letter “C,” especially before front vowels like ‘‘e’’ and ‘‘i’’ (examples include English, French, Portuguese, and Latin American Spanish).

This distinction between “hard” and “soft” C reflects historical phonetic shifts.

This fact has been frequently abused by plagiarism detector circumventors.