Iota ι

Iota is the ninth Greek letter, from Phoenician yod ('hand'); its value is 10. As the smallest and simplest Greek letter it became proverbial for the least possible amount: the English 'not one iota' and the biblical 'not one jot' (Matthew 5:18) both invoke it. The Greek letters doubled as numerals in the Milesian (alphabetic) system, in which each letter carried a fixed value; the practice of summing a word's letters into a number, called isopsephy, is the Greek counterpart of Hebrew gematria and appears in inscriptions, the Greek Magical Papyri and early Christian texts. Iota's Phoenician ancestry places it in a borrowing whose exact point of contact, somewhere among Al Mina, Cyprus, Crete and Euboea in the Aegean world, is still disputed, though the borrowing itself, conventionally dated to around the 8th century BCE, is agreed to be the ancestor of every European alphabet still in use, including the Latin one covered elsewhere in this atlas.

The Greeks' own contribution was to give vowels dedicated letters of their own, something the consonant-only Phoenician script never did. Its isopsephy value of 10 belongs to the Milesian alphabetic numeral system, which also needed three further, otherwise obsolete letters, digamma (also called stigma), koppa and sampi, to cover every value from 1 up to 900; none of the three survives among the 24 letters in ordinary use today.

Iota is the smallest letter in the Greek alphabet, written as a single unadorned stroke, and that physical smallness gave rise to one of the most durable idioms drawn from any letter in this atlas: the Gospel of Matthew (5:18), in a passage about the permanence of religious law, states that not one iota or one stroke of a letter will pass from it, using the letter's minimal shape as a figure for the smallest conceivable unit of meaning; the English phrase not one iota, meaning not the slightest amount, descends directly from that verse.

In Byzantine Greek pronunciation, iota also became one of several vowels and vowel combinations that converged on the same simple i sound, a merger called iotacism, which is why several distinct ancient Greek vowels and diphthongs are all pronounced alike in modern Greek. Iota has only modest modern technical use, chiefly as a variable name in mathematics and programming where a short, unclaimed symbol is convenient, and astronomers, following the Bayer star-naming convention of 1603, use Iota to mark a constellation's ninth-brightest star. In the Milesian numeral system covered elsewhere in this atlas, iota carries the plain value of ten, one of the least remarked-upon assignments in that entire numbering scheme.