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.