Omicron

Use

In addition to its use as an alphabetic letter, omicron is occasionally used in technical notation, but its use is limited since both upper case and lower case (Ο ο) are indistinguishable from the Latin letter "o" (O o) and difficult to distinguish from the Arabic numeral "zero" (0).

Mathematics

The big-O symbol was introduced by Paul Bachmann in 1894 and popularized by Edmund Landau in 1909, originally standing for "order of" ("Ordnung") and being thus a Latin letter, was apparently viewed by Donald Knuth in 1976 as a capital Omicron, probably in reference to his definition of the symbol (capital) Omega. Neither Bachmann nor Landau ever call it "Omicron", and the word "Omicron" appears just once in the title of Knuth's paper.

Greek numerals

Main article: Greek numerals

There were several systems for writing numbers in Greek; the most common form used in late classical era used omicron (either upper or lower case) to represent the value 70.

More generally, the letter omicron is used to mark the fifteenth ordinal position in any Greek-alphabet marked list. So, for example, in Euclid's Elements, when various points in a geometric diagram are marked with letters, it is effectively the same as marking them with numbers, each letter representing the number of its place in the standard alphabet.{{efn Greek letters-as-numbers used an older Greek alphabet with three more otherwise unused letters, two of them re‑instated in their old locations, early in the alphabet. So positions higher than 5th place (ε) were shifted from the standard alphabet; 5th place was marked with normal fifth letter epsilon (ε). The 6th letter in the conventional alphabet, that normally follows ε is ζ (zeta) but the number 6 was represented a revived ancient letter ϝ (digamma), followed by ζ which was pushed up from 6th to its ancient position (7th) to represent the number 7. All of the letters after ζ were likewise shifted up one place, until the second ancient letter koppa, (ϙ), was reached; it fell between π and ρ. Every letter from ρ to ω was shifted two places past its conventional ordinal position. Last place coming right after omega (ω, 800) was sampi (ϡ) which represented 900. (From that point, the system restarted, with a new tick-mark, at ͵α. The tick-mark was put in a different place (͵α rather than α) to show that the letter represented a multiple of 1,000 rather than 1.) From Euclid up to the 19th century, mathematical and technical diagrams were habitually marked sequentially with letters (or numbers), whereas in modern mathematical and scientific diagrams, it is much more common to choose for markers letters that might remind readers of the word used to describe the item in question. For example, Feynman diagrams in particle physics label the positions of particles with the first letter of their name, either in the Latin or Greek alphabet. So p, n, and e , represent the position on a diagram of a proton, neutron, and electron, respectively. The neutrino is represented by ν (Greek "nu"), since the Latin letter "n" is reserved for the neutron.

Astronomy

Omicron is used to designate the fifteenth star in a constellation group, its ordinal placement an irregular function of both magnitude and position. |access-date=8 February 2016 |access-date=8 February 2016 Such stars include Omicron Andromedae, Omicron Ceti (Mira), and Omicron Persei.

In Claudius Ptolemy's () Almagest, tables of sexagesimal numbers 1 ... 59 are represented in the conventional manner for Greek numbers:{{efn Sexagesimal Greek numbers in the Almagest are conventional: and . Notice that ancient digamma (ϝ) is used for 6 instead of zeta (ζ, which is used for 7) . Adjacent number-letters add, so all the other numbers are made by letter pairs, such as . The number 59 (′νθ) is the largest value used in any single number cell in sexagesimal. That leaves xi (ξ) and the letters following it (ξ ο π ϙ ρ σ τ υ φ χ ψ ω ϡ) free for other use: Ptolemy picked ′ο, which normally was used for 70, to mark empty (zero) cells, perhaps because the word for "nothing", οὐδέν starts with an omicron.

Medicine

Main article: SARS-CoV-2 Omicron variant

The World Health Organization (WHO) uses the Greek alphabet to describe variants of concern of SARS‑CoV‑2, the virus which causes COVID-19. On November 26, 2021, Omicron was assigned to the B.1.1.529 variant of concern.

History

In the earliest Greek inscriptions, only five vowel letters A E I O Y were used. Vowel length was undifferentiated, with O representing both the short vowel /o/ and the long vowels /o:/ and /ɔː/. Later, in classical Attic Greek orthography, the three vowels were represented differently, with O representing short /o/, the new letter Ω representing long /ɔː/, and the so-called "spurious diphthong" OY representing long /o:/.

Although the Greeks took the character O from the Phoenician letter `ayin, they did not borrow its Phoenician name. Instead, the name of the letter O in classical Attic times was simply the long version of its characteric sound: οὖ (pronounced /o:/) (that of Ω was likewise ὦ).{{efn| This is confirmed by the text of the so-called Letter Tragedy of the fifth-century BCE comic poet Callias, and also by a passage in Plato's Cratylus, where Socrates states: :[W]hen we speak of the letters of the alphabet, you know, we speak their names, not merely the letters themselves, except in the case of four: E, Y, O, and Ω.

Mispronunciation

During the early outbreak of the Omicron variant of COVID-19, many people unfamiliar with the Greek alphabet mispronounced Omicron as "Omnicron" due to the prevalence of the prefix "Omni-" in many English words.

Unicode

Greek omicron / Coptic O

These characters are used only as mathematical symbols. Stylized Greek text should be encoded using the normal Greek letters, with markup and formatting to indicate text style:

Footnotes

References

References

1. {{OED. omicron
2. [http://www.quinapalus.com/gr0.1.html The Greek Alphabet]
3. Knuth, Donald. (April–June 1976). "Big Omicron and big Omega and big Theta". SIGACT News.
4. (2021-06-09). "Embrace the WHO's new naming system for coronavirus variants". Nature.
5. Sihler, Andrew. (1995). "New Comparative Grammar of Greek and Latin". Oxford University Press.
6. Allen, W. Sidney. (1987). "Vox Graeca". Cambridge University Press.
7. [[Plato]]. "Cratylus".
8. (November 29, 2021). "It's 'omicron,' not 'omnicron': COVID variant's spelling doesn't have two Ns".
9. "'Omni is everywhere': Why do so many people struggle to say Omicron? | Language | the Guardian".
10. (2015). "Greek and Coptic (Range: 0370–03FF)". [[Unicode Consortium.
11. (2015). "Mathematical Alphanumeric Symbols (Range: 1D400–1D7FF)". [[Unicode Consortium.