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Οmicrοn（/ˈoʊmɪkrɒn, ˈɒmɪkrɒn, oʊˈmaɪkrɒn/; 大写Ο，小写ο，中文音译：奥米克戎、奥密克戎、歐米克隆）是第15个希腊字母。在希腊数字系统中，它的数值为70。这个字母来源于腓尼基字母ayin：。在古希臘語中，οmicrοn代表的发音是[o]，与omega [ɔː]和ου [oː]形成对立。在现代希腊语中，οmicrοn代表中後圓唇元音/o̞/ ，与omega同音。由οmicrοn产生的字母包括罗马字母O和西里尔字母O。 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。 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，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。 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。 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。这样的恒星包括Omicron Andromedae、Omicron Ceti和Omicron Persei。 在克劳狄乌斯·托勒密（约约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表示：′α ... ′νθ。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（ο）类似于现代阿拉伯数字的零（0）。 2021年11月26日，世界卫生组织宣布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Omicron。B.1.1.529变异株于2021年11月24日在南非首次被测序。 Greek Omicron / Coptic O Mathematical Omicron 这些字符只作为数学符号使用。风格化的希腊文应使用正常的希腊字母进行编码，用标记和文本格式来表示文本风格。 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. Ever 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. Sexagesimal Greek numbers in the Almagest are conventional:   1 2 3 4 5 6 7 8 9  =  ′α ′β ′γ ′δ ′ε ′ϝ ′ζ ′η ′θ . Notice that ancient digamma (ϝ) is used for  6  instead of zeta (ζ, which is used for 7) ;   10 20 30 40 50  =  ′ι ′κ ′λ ′μ ′ν . Adjacent number-letters add, so all the other numbers are made by letter pairs, such as  29 30 31  =  ′κθ ′λ ′λα . The number 59 (′νθ) is the largest value used in a single 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. omicron. 牛津英語詞典 (第三版). 牛津大學出版社. 2005-09 （英语）.  希腊字母的汉字规范译音. 中国科技术语. 2003, 5 (03) [2021-11-30]. ISSN 1673-8578. （原始内容存档于2021-09-21）. 奥米克戎  Knuth, Donald. Big Omicron and big Omega and big Theta (PDF). SIGACT News. April–June 1976, 8 (2): 18–24 [2021-11-28]. S2CID 5230246. doi:10.1145/1008328.1008329. （原始内容存档 (PDF)于2021-11-30）.  Martin, Martha Evans. The Friendly Stars 1st. New York: Harper & Brothers Publishers. 1907: 135 [8 February 2016].  Wilk, Stephen R. Medusa: Solving the Mystery of the Gorgon 1st. New York, NY; London, UK: Oxford University Press. 2007: 201 [8 February 2016]. ISBN 9780199887736. （原始内容存档于2022-01-30）.  Classification of Omicron (B.1.1.529): SARS-CoV-2 Variant of Concern. World Health Organization. [26 November 2021]. （原始内容存档于2021-11-26）.  Greek and Coptic (Range: 0370–03FF) (PDF). The Unicode Standard, Ver. 8.0. Unicode, Inc. 2015 [8 February 2016]. （原始内容存档 (PDF)于2022-02-15）.  Mathematical Alphanumeric Symbols (Range: 1D400–1D7FF) (PDF). The Unicode Standard, Ver. 8.0. Unicode, Inc. 2015 [8 February 2016]. （原始内容存档 (PDF)于2021-10-16）.  维基词典中的词条「Ο」 维基词典中的词条「ο」