omicron

Definition

The 15th letter of the Classical and Modern Greek alphabets (16th in Ancient and Old Greek), used in ordering lists as in naming (astronomy) the 15th star of a constellation or (epidemiology) the 15th discovered major variant of a disease.

Etymology

From Latin omicron, from Koine Greek ὂ μῑκρόν (ò mīkrón, “little o”), named in contrast with omega (“big o”). The uncommon form omicra is similarly borrowed from Latin and Greek. The use for designating stars in a constellation—typically in order of apparent brightness—began with Johann Bayer's 1603 Uranometria.

Example Sentences

• "Your Majestie knows that unfortunate I [...] was the first who when I published my Poem of Italia Liberata endeavoured to bring the Omicron, Eupselon, Omega, and other Greek Letters, which I thought very requisite for that language, into my own Tongue;"
• "The E serves both for the Epsilon and Eta; the O, both for the Omicron and Omega, and likewise for the dipthong OΥ."
• "... They include Mira itself (omicron Ceti) which can be seen shortly before dawn."