Omicron (, ; uppercase Ο, lowercase ο, ) is the fifteenth letter of the

Greek alphabet The Greek alphabet has been used to write the Greek language since the late 9th or early 8th century BC. It was derived from the earlier Phoenician alphabet, and is the earliest known alphabetic script to systematically write vowels as wel ...

. This letter is derived from the Phoenician letter

ayin ''Ayin'' (also ''ayn'' or ''ain''; transliterated ) is the sixteenth letter of the Semitic scripts, including Phoenician ''ʿayin'' 𐤏, Hebrew ''ʿayin'' , Aramaic ''ʿē'' 𐡏, Syriac ''ʿē'' ܥ, and Arabic ''ʿayn'' (where it is si ...

. In

classical Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archa ...

, omicron represented the close-mid back rounded vowel in contrast to ''

omega Omega (, ; uppercase Ω, lowercase ω; Ancient Greek ὦ, later ὦ μέγα, Modern Greek ωμέγα) is the twenty-fourth and last letter in the Greek alphabet. In the Greek numerals, Greek numeric system/isopsephy (gematria), it has a value ...

'' which represented the open-mid back rounded vowel and the digraph ''ου'' which represented the long close-mid back rounded vowel . In

modern Greek Modern Greek (, or , ), generally referred to by speakers simply as Greek (, ), refers collectively to the dialects of the Greek language spoken in the modern era, including the official standardized form of the language sometimes referred to ...

, both omicron and omega represent the mid back rounded vowel or . Letters that arose from omicron include Roman O and Cyrillic O and Ю. The word literally means "little O" (''o mikron'') as opposed to "great O" (''ō mega''). In the system of

Greek numerals Greek numerals, also known as Ionic, Ionian, Milesian, or Alexandrian numerals, is a numeral system, system of writing numbers using the letters of the Greek alphabet. In modern Greece, they are still used for ordinal number (linguistics), ordi ...

, omicron has a value of 70.

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 The Latin script, also known as the Roman script, is a writing system based on the letters of the classical Latin alphabet, derived from a form of the Greek alphabet which was in use in the ancient Greek city of Cumae in Magna Graecia. The Gree ...

"o" (O o) and difficult to distinguish from the

Arabic numeral The ten Arabic numerals (0, 1, 2, 3, 4, 5, 6, 7, 8, and 9) are the most commonly used symbols for writing numbers. The term often also implies a positional notation number with a decimal base, in particular when contrasted with Roman numerals. ...

"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 Donald Ervin Knuth ( ; born January 10, 1938) is an American computer scientist and mathematician. He is a professor emeritus at Stanford University. He is the 1974 recipient of the ACM Turing Award, informally considered the Nobel Prize of comp ...

in 1976 as a capital Omicron, probably in reference to his definition of the symbol (capital)

Omega Omega (, ; uppercase Ω, lowercase ω; Ancient Greek ὦ, later ὦ μέγα, Modern Greek ωμέγα) is the twenty-fourth and last letter in the Greek alphabet. In the Greek numerals, Greek numeric system/isopsephy (gematria), it has a value ...

. Neither Bachmann nor Landau ever call it "Omicron", and the word "Omicron" appears just once in the title of Knuth's paper.

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 Euclid (; ; BC) was an ancient Greek mathematician active as a geometer and logician. Considered the "father of geometry", he is chiefly known for the '' Elements'' treatise, which established the foundations of geometry that largely domina ...

'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.

Astronomy

Omicron is used to designate the fifteenth star in a constellation group, its ordinal placement an irregular function of both magnitude and position. Such stars include Omicron Andromedae, Omicron Ceti, and Omicron Persei. In Claudius Ptolemy's () '' Almagest'', tables of

sexagesimal Sexagesimal, also known as base 60, is a numeral system with 60 (number), sixty as its radix, base. It originated with the ancient Sumerians in the 3rd millennium BC, was passed down to the ancient Babylonians, and is still used—in a modified fo ...

numbers are represented in the conventional manner for Greek numbers:. Since the letter omicron hich represents () in the standard systemis not used in

, it is repurposed to represent an empty number cell. In some copies, zero cells were just left blank (nothing there, value is zero), but to avoid copying errors, positively marking a zero cell with omicron was preferred, for the same reason that blank cells in modern tables are sometimes filled-in with a long dash (—). Both an omicron and a dash imply that ''"this is not a mistake, the cell is actually supposed to be empty."'' By coincidence, the ancient zero-value omicron () resembles a modern Hindu-Arabic zero ().

Medicine

The

World Health Organization The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Gen ...

(WHO) uses the Greek alphabet to describe variants of concern of SARS‑CoV‑2, the virus which causes

COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by the coronavirus SARS-CoV-2. In January 2020, the disease spread worldwide, resulting in the COVID-19 pandemic. The symptoms of COVID‑19 can vary but often include fever ...

. On November 26, 2021, Omicron was assigned to the B.1.1.529

variant of concern Variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are viruses that, while similar to the original, have genetic changes that are of enough significance to lead virologists to label them separately. SARS-CoV-2 is the v ...

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: (pronounced /o:/) (that of Ω was likewise ). By the second and third centuries AD, distinctions between long and short vowels began to disappear in pronunciation, leading to confusion between O and Ω in spelling. It was at this time that the new names of ("small O") for O ("great O") for Ω were introduced.

Mispronunciation

During the early outbreak of the Omicron variant of COVID-19, many people unfamiliar with the entire Greek alphabet (or simply lacking the ability to pronounce or sound out words using

phonetics Phonetics is a branch of linguistics that studies how humans produce and perceive sounds or, in the case of sign languages, the equivalent aspects of sign. Linguists who specialize in studying the physical properties of speech are phoneticians ...

) mispronounced Omicron as "Omnicron" due to the unfamiliarity of the letter, and the use of the prefix "Omni-" in many 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

External links

{{Wiktionary, Ο, ο Greek letters Vowel letters