Ḍād (ﺽ) is the fifteenth letter of the Arabic alphabet, one of the six letters not in the twenty-two akin to the Phoenician alphabet (the others being ṯāʾ, ḫāʾ, ḏāl, ẓāʾ, ġayn). In name and shape, it is a variant of ṣād. Its numerical value is 800 (see Abjad numerals). It is related to the Ancient North Arabian 𐪓, South Arabian 𐩳.
The letter symbol itself is a derivation, by addition of a diacritic dot, from ص ṣād (representing /sˤ/).
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. It is related to the Ancient North Arabian 𐪎, South Arabian 𐩮, and Ge'ez ጸ. The corresponding letter of the Ugaritic alphabet is 𐎕 ṣade.
Its oldest phonetic value is debated, although there is a variety of pronunciations in different modern Semitic languages and their dialects. It represents the coalescence of three Proto-Semitic "emphatic consonants" in Canaanite. Arabic, which kept the phonemes separate, introduced variants of ṣād and ṭāʾ to express the three (see ḍād, ẓāʾ). In Aramaic, these emphatic consonants coalesced instead with ʿayin and ṭēt, respectively, thus Hebrew ereṣ ארץ (earth) is araʿ ארע in Aramaic.