编辑“︁Ο”︁（章节）

==用处==
除了作为字母使用外，omicron偶尔也用于技术符号，但其用途有限，因为大写和小写（Ο ο）都与[[拉丁字母]]O无法区分，也难以与[[阿拉伯数字]]0区别。

===数学===

由Paul Bachmann在1894年提出、[[愛德蒙·蘭道]]在1909年推广的[[大O符号]]，最初代表“order of”（"Ordnung"，阶），因此是一个[[拉丁字母]]，显然在1976年被[[高德纳]]视为大写的Omicron<ref name="knuth">{{cite journal |first=Donald |last=Knuth |url=http://www.phil.uu.nl/datastructuren/10-11/knuth_big_omicron.pdf |title=Big Omicron and big Omega and big Theta |journal=SIGACT News |date=April–June 1976 |volume=8 |issue=2 |pages=18–24 |doi=10.1145/1008328.1008329 |s2cid=5230246 |access-date=2021-11-28 |archive-date=2021-11-30 |archive-url=https://web.archive.org/web/20211130005215/https://www.phil.uu.nl/datastructuren/10-11/knuth_big_omicron.pdf |dead-url=no }}</ref>，可能是参考了他对符号（大写）[[Omega]]的定义。Bachmann和蘭道都没有称它为“Omicron”，“Omicron”这个词在克努特的论文中只出现过一次，而且只是在标题中。

===希腊数字===
{{main|希腊数字}}
在希腊语中，有几种数字书写系统；在古典时代后期，最常见的形式是用omicron（大写或小写）来代表70这个数值。

更为普遍的是，在任何希腊字母标记的列表中，字母omicron都被用来标记第15个序数的位置。因此，例如在[[欧几里得]]的《[[几何原本]]》中，当[[几何学|几何]]图中的各个点用字母标记时，实际上与用数字标记相同，每个字母代表其在标准字母表中的位置数字。{{efn
|name=ordinal_greek_letters|
Greek [[希腊数字|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 ({{mvar|[[Ε|&epsilon;]]}}) were shifted from the standard alphabet; 5th place was marked with normal fifth letter [[epsilon]] ({{math|[[Ε|&epsilon;]]}}). The 6th letter in the conventional alphabet, that normally follows  {{math|[[Ε|&epsilon;]]}}  is  {{math|[[Ζ|&zeta;]]}}  ([[zeta]]) but the ''number'' 6 was represented a revived ancient letter {{mvar|&prime;[[Ϝ|ϝ]]}} ([[digamma]]), followed by {{math|&prime;[[Ζ|&zeta;]]}} which was pushed up from 6th to its ancient position (7th) to represent the number 7. All of the letters after {{math|[[Ζ|&zeta;]]}} were likewise shifted up one place, until the second ancient letter [[koppa (letter)|koppa]], ({{math|[[Ϙ|ϙ]]}}), was reached; it fell between {{math|[[Π|&pi;]]}} and {{math|[[Ρ|&rho;]]}}. Ever letter from [[Ρ|&rho;]] to [[Ω|&omega;]] was shifted ''two'' places past its conventional ordinal position. Last place coming right after [[omega]] ({{math|[[Ω|&omega;]]}}, 800) was [[Ͳ|sampi]] ({{math|ϡ}}) which represented 900. (From that point, the system restarted, with a new tick-mark, at {{math|'''{{big|͵}}'''[[Α|α]]}}. The tick-mark was put in a different place ({{math|'''{{big|͵}}'''[[Α|α]]}} rather than {{math|&prime;[[Α|α]]}}) to show that the letter represented a multiple of 1,000 rather than 1.)
}}{{efn
|name=diagrams|
From [[几何原本|Euclid]] up to the 19th&nbsp;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, [[费曼图|Feynman diagram]]s in [[粒子物理學|particle physics]] label the positions of particles with the first letter of their name, either in the Latin or Greek alphabet. So &nbsp;{{math|p}}, {{math|n}}, and {{math|e}}&nbsp;, represent the position on a diagram of a &nbsp;[[質子|<u>p</u>roton]], [[中子|<u>n</u>eutron]], and [[电子|<u>e</u>lectron]],&nbsp; respectively. The [[中微子|<u>n</u>eutrino]] is represented by {{mvar|[[Ν|&nu;]]}} (Greek [[Ν|"nu"]]), since the Latin letter "{{math|n}}" is reserved for the [[中子|<u>n</u>eutron]].
}}

===天文学===
Omicron用于指定一个星座组中的第十五颗星，它的序数位置是星等和位置的不规则函数。<ref name="martin">
{{cite book
 |last=Martin |first=Martha Evans
 |year=1907
 |title=The Friendly Stars
 |edition=1st |page=[https://archive.org/details/friendlystars01martgoog/page/n154 135]
 |publisher=[[Harper (publisher)|Harper & Brothers Publishers]]
 |location=New York
 |url=https://archive.org/details/friendlystars01martgoog
 |access-date=8 February 2016
}}
</ref><ref name="wilk">{{cite book
 |last=Wilk
 |first=Stephen R.
 |year=2007
 |title=Medusa: Solving the Mystery of the Gorgon
 |edition=1st
 |page=201
 |publisher=[[牛津大學出版社|Oxford University Press]]
 |location=New York, NY; London, UK
 |isbn=9780199887736
 |url=https://books.google.com/books?id=OnHO4orvz18C&pg=PT201
 |access-date=8 February 2016
 |archive-date=2022-01-30
 |archive-url=https://web.archive.org/web/20220130234442/https://books.google.com/books?id=OnHO4orvz18C&pg=PT201
 |dead-url=no
 }}</ref>这样的恒星包括[[车府增十六|Omicron Andromedae]]、[[蒭藁增二|Omicron Ceti]]和[[英仙座ο|Omicron Persei]]。

在[[克劳狄乌斯·托勒密]]（约{{circa|100–170}}）的《[[天文學大成]]》中，1 ... 59的[[六十進制]]数字表是以希腊数字的传统方式{{efn
|name=why_omicron_is_available| 
[[Sexagesimal]] [[希腊数字|Greek numbers]] in the ''[[天文學大成|Almagest]]'' are [[希腊数字|conventional]]: &nbsp; 1 2 3 4 5 6 7 8 9  {{math|&nbsp;{{=}}&nbsp; &prime;α  &prime;β  &prime;γ  &prime;&delta;  &prime;&epsilon;    &prime;''ϝ''  &prime;&zeta;  &prime;&eta;  &prime;θ}}&nbsp;. Notice that ancient [[digamma]] ({{mvar|ϝ}}) is used for &nbsp;6&nbsp; instead of [[zeta]] ({{math|&zeta;}}, which is used for 7)&nbsp;; &nbsp; 10  20  30  40  50 {{math|&nbsp;{{=}}&nbsp; &prime;&iota;  &prime;&kappa;  &prime;λ  &prime;&mu;  &prime;&nu;}}&nbsp;. Adjacent number-letters add, so all the other numbers are made by letter pairs, such as &nbsp;29  30  31 {{math| &nbsp;{{=}}&nbsp; &prime;&kappa;θ  &prime;λ  &prime;λα}}&nbsp;. The number 59 ({{math|&prime;&nu;θ}}) is the largest value used in a single cell in [[六十進制|sexagesimal]]. That leaves [[Ξ|xi]] ({{math|&xi;}}) and the letters following  it &nbsp;{{math| &xi; &omicron; &pi; ϙ &rho; &sigma; &tau; &upsilon; &phi; &chi; &psi; &omega; ϡ}}&nbsp; free for other use: [[克劳狄乌斯·托勒密|Ptolemy]] picked {{math|&nbsp;&omicron;&nbsp;}}, which normally was used for 70, to mark empty (zero) cells, perhaps because the word for "nothing", {{math|οὐδέν}} starts with an omicron.
}}表示：{{math|&prime;α}} ... {{math|&prime;&nu;θ}}。由于字母omicron[在标准系统中代表70（′ο）]在六进制中没有使用，它被重新用于代表一个空的数字单元。在某些版本中，该单元格只是留有空白（那里没有东西=数值为零），但为了避免复制错误，人们倾向于用omicron标记一个零单元格，就像现代表格中的空白单元格用破折号（-）填充一样。Omicron和破折号都意味着“这不是一个错误，这个单元格实际上应该是空的”。巧合的是，古代的零值omicron（{{math|&omicron;}}）类似于现代[[阿拉伯数字]]的零（0）。

===用以命名冠狀病毒2型的變異株 ===
{{main|嚴重急性呼吸道症候群冠狀病毒2型Omicron變異株}}
2021年11月26日，[[世界卫生组织]]宣布[[2019冠状病毒病|COVID-19]]的一个新的变异株值得关注，根据世卫组织的命名系统命名为[[嚴重急性呼吸道症候群冠狀病毒2型Omicron變異株|Omicron]]。B.1.1.529变异株于2021年11月24日在[[南非]]首次被测序。<ref>{{cite web
 |title=Classification of Omicron (B.1.1.529): SARS-CoV-2 Variant of Concern
 |url=https://www.who.int/news/item/26-11-2021-classification-of-omicron-(b.1.1.529)-sars-cov-2-variant-of-concern
 |publisher=World Health Organization
 |access-date=26 November 2021
 |archive-date=2021-11-26
 |archive-url=https://web.archive.org/web/20211126180836/https://www.who.int/news/item/26-11-2021-classification-of-omicron-%28b.1.1.529%29-sars-cov-2-variant-of-concern
 |dead-url=no
 }}</ref>