The Arabic letter س sīn /s/ (Arabic: سِينْ, sīn or seen /siːn/) is the 12th letter in the common Hijā'i order, and the 15th letter in the Abjadi order (corresponding to the 15th letter Phoenician letter Samekh). Based on Semitic linguistics, Samekh has no surviving descendant in the Arabic alphabet, and that sīn is derived from Phoenician šīn 𐤔 rather than Phonecian sāmek 𐤎, but unlike the Aramaic 𐡔‎‎ sīn/šīn and the Hebrew ש‎ sīn/šīn, Arabic س sīn /s/ is considered a completely separate letter from ش šīn /ʃ/, and is written thus:

The history of the letters expressing sibilants in the various Semitic alphabets is somewhat complicated, due to different mergers between Proto-Semitic phonemes. As usually reconstructed, there are four plain Proto-Semitic coronal voicelessfricative phonemes (not counting emphatic ones) that evolved into the various voiceless sibilants of its daughter languages, as follows:

In the Maghrebian abjad sequence (quoted in apparently earliest authorities and considered older by Michael Macdonald):