Shin (letter) languages, as follows: In the Arabic alphabet, ' is at the original (21st) position in Abjadi order. A letter variant ' takes the place of Samekh at 15th position. "" represents , and is the 13th letter of the modern alphabet order and is written thus: The Arabic letter "šīn" was an acronym for "something" ( "šayʾ(un)" ) meaning the unknown in algebraic equations. In the transcription into Spanish, the Greek letter "chi" (χ) was used which was later transcribed into Latin "x". According to some sources, this is the origin of "x" used for the unknown in the equations.
Delta (letter) Delta (letter) Delta (uppercase Δ, lowercase δ or 𝛿; "délta", ) is the fourth letter of the Greek alphabet. In the system of Greek numerals it has a value of 4. It was derived from the Phoenician letter dalet 𐤃, Letters that come from delta include Latin D and Cyrillic Д. A river delta (originally, the Nile River delta) is so named because its shape approximates the triangular uppercase letter delta. Despite a popular legend, this use of the word "delta" was not coined by Herodotus. In Ancient Greek, delta represented a voiced dental plosive . In Modern Greek, it