Sin is the twelfth letter of the modern Arabic order and the fifteenth of the older abjad order, from which it takes the numeral value sixty. It is written as three short teeth running into a shallow bowl that drops below the line, and it joins on both sides, keeping only the three teeth at the beginning and in the middle of a word. In several hands the teeth are flattened into a single horizontal stroke, a variation that is a matter of style rather than of spelling. The same skeleton carrying three dots above is shin.
Sin is a sun letter, so the lam of the definite article assimilates to it. Its sound is the voiceless alveolar sibilant, the s of English, and it is distinguished from the emphatic sad by the position of the tongue rather than by any mark on the page.
Its place in the inherited sequence is where the Semitic alphabets become difficult to line up. Sin holds the fifteenth position and the numeral value sixty, which in Hebrew belong to samekh, while its name resembles that of shin. The sibilant letters underwent shifts of sound and of name across the Semitic languages that scholars reconstruct in more than one way, and no single mapping of Arabic sibilants onto Hebrew ones satisfies both the names and the values. The atlas records the position and the value, which are stable, and does not assert a name derivation for sin. Sin appears among the fourteen letters that stand disjoined at the head of certain suras.