Shin (also spelled Šin (šīn) or Sheen) literally means "sharp"; It is the twenty-first letter in many Semitic abjads, including Phoenician 𐤔, Aramaic/Hebrew ש, and Arabic ش (in abjadi order, 13th in modern order). Its sound value is a voiceless sibilant, [ʃ] or [s].
The Phoenician letter gave rise to the Greek Sigma (Σ) (which in turn gave Latin S and Cyrillic С), and the letter Sha in the Glagolitic and Cyrillic scripts (Ⱎ, Ш).
The South Arabian and Ethiopian letter Śawt is also cognate.
The Phoenician šin letter expressed the continuants of two Proto-Semitic phonemes, and may have been based on a pictogram of a tooth (in modern Hebrew shen). The Encyclopaedia Judaica, 1972, records that it originally represented a composite bow.
The history of the letters expressing sibilants in the various Semitic alphabets is a bit complicated, due to different mergers between Proto-Semitic phonemes. As usually reconstructed, there are five Proto-Semitic phonemes that evolved into various voiceless sibilants in daughter languages, as follows: