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.
History of the Greek alphabet Phoenician values, but with different forms: as the Greek letter digamma for the consonant , and as the letter upsilon for the vowel . Upsilon was added at the end of the alphabet, perhaps to avoid upsetting the alphabetic order that was used in Greek numerals. Phoenician "hē" had been used as a "mater lectionis" for both and in addition to , but in Greek it was restricted to , following the acrophonic principle; its value was instead written with the letter "’āleph", while Greek was written with "ḥeth". All Phoenician letters had been acrophonic, and they remained so in