Shin (also spelled Šin (šīn) or Sheen) literally means "teeth", "press", and "sharp"; It is the twenty-first letter of the Semitic abjads, including Phoenician Shin Phoenician Hebrew Shin ש, Aramaic Shin Syriac Shin ܫ, and Arabic Shin 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 (Glagolitic, Ш).
Shin also stands for the word Shaddai, a name for God. Because of this, a kohen (priest) forms the letter Shin with his hands as he recites the Priestly Blessing. In the mid 1960s, actor Leonard Nimoy used a single-handed version of this gesture to create the Vulcan hand salute for his character, Mr. Spock, on Star Trek.
The letter Shin is often inscribed on the case containing a mezuzah, a scroll of parchment with Biblical text written on it. The text contained in the mezuzah is the Shema Yisrael prayer, which calls the Israelites to love their God with all their heart, soul and strength. The mezuzah is situated upon all the doorframes in a home or establishment. Sometimes the whole word Shaddai will be written.