Omicron ο

Omicron is the fifteenth Greek letter, from Phoenician ayin ('eye'); its value is 70. Its name means 'small o' (o-micron), distinguishing the short o from the long omega ('great o'). Omicron has no significant independent esoteric tradition beyond its place in isopsephy. 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. Omicron'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 70 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.

Omicron's name, meaning small o, already distinguishes it in Greek from omega, the great o, discussed elsewhere in this atlas; both letters write the same vowel sound in modern Greek, a distinction that survives in name only since the ancient short-versus-long vowel contrast the two letters once marked has been lost in the modern language. Omicron had a comparatively low profile in general modern usage until November 2021, when the World Health Organization, following its 2021 system of naming coronavirus variants after Greek letters, designated the heavily mutated B.1.1.529 lineage Omicron, after skipping the two preceding letters, nu and xi, for reasons covered elsewhere in this atlas. The Omicron variant went on to become the dominant global strain within months of its naming, making omicron, almost overnight, one of the most frequently spoken and written Greek letter names in the world, entirely apart from its ancient sound value or any classical or scriptural association.

Astronomers, following the older Bayer star-naming convention of 1603, also use Omicron for a constellation's fifteenth-brightest star, a far quieter and much older use of the same letter. In the Milesian numeral system, discussed elsewhere in this atlas, omicron carries the value seventy, entirely unconnected to either its name or its sudden 21st-century prominence.