Tsade (also spelled ṣade, ṣādē, ṣaddi, ṣad, tzadi, sadhe, tzaddik) is the eighteenth letter of the Semitic abjads, including Phoenician ṣādē 𐤑, Hebrew ṣādī צ, Aramaic ṣāḏē 𐡑, Syriac ṣāḏē ܨ, Ge'ez ṣädäy ጸ, and Arabic ṣād ص.
Arabic, which kept the phonemes separate, introduced variants of ṣād and ṭāʾ to express the three (see ḍād, ẓāʾ).
The Phoenician letter is continued in the Greek san (Ϻ) and possibly sampi (Ϡ), and in Etruscan 𐌑 Ś.
The phoneme is not native to Persian, Ottoman Turkish, or Urdu, and its pronunciation in Arabic loanwords in those languages is not distinguishable from س or ث, all of which are pronounced [s].
Often, words that have ظ ẓāʾ, ص ṣād, and ض ḍād in Arabic have cognates with צ tsadi in Hebrew.
Alternatively, it can be called tsadik or ṣadik, spelled צָדִּיק, influenced by its Yiddish name tsadek and the Hebrew word tzadik.
Ṣadi is also one of the seven letters that receive special crowns (called tagin) when written in a Sefer Torah.