O

In English, the name of the letter is the "long O" sound, pronounced {{IPAc-en|'|oʊ}}. In most other languages, its name matches the letter's pronunciation in open syllables.

File:Pronunciation of the name of the letter ⟨o⟩ in European languages.png

File:Newes ABC Buchlein MET DP855603.jpg or early Baroque design of an O, from 1627]]

Its graphic form has remained fairly constant from Phoenician times until today. The name of the Phoenician letter was ʿeyn, meaning "eye", and its shape originates simply as a drawing of a human eye (possibly inspired by the corresponding Egyptian hieroglyph, {{Cf.}}Proto-Sinaitic script). Its original sound value was that of a consonant, probably {{IPAblink|ʕ}}, the sound represented by the cognate Arabic letter ع ʿayn.{{Cite web |title=Evolution of Alphabets |url=https://webspace.ship.edu/cgboer/evolalpha.html |access-date=2024-01-03 |website=webspace.ship.edu}}

The use of this Phoenician letter for a vowel sound is due to the early Greek alphabets, which adopted the letter "omicron" to represent the vowel {{IPA|/o/}}. The letter was adopted with the value in the Old Italic alphabets, including the early Latin alphabet. In Greek, a variation of the form later came to differentiate this long sound (omega, meaning "large O") from the short o (Omicron, meaning "small o"). The Greek omicron gave rise to the corresponding Cyrillic letter O.{{Cite web |title=Cyrillic script |url=https://www.omniglot.com/writing/cyrillic.htm |access-date=2024-01-03 |website=www.omniglot.com}}

The letter {{angbr|o}} is the fourth most common letter in the English alphabet.{{cite web|url=https://pi.math.cornell.edu/~mec/2003-2004/cryptography/subs/frequencies.html|title=Frequency Table|website=www.math.cornell.edu}} Like the other English vowel letters, it has associated "long" and "short" pronunciations. The "long" {{angbr|o}} as in boat is actually most often a diphthong {{IPAc-en|oʊ}} (realized dialectically anywhere from {{IPA|[o]}} to {{IPA|[əʊ]}}). In English, there is also a "short" {{angbr|o}} as in fox, {{IPAc-en|ɒ}}, which sounds slightly different in different dialects. In most dialects of British English, it is either an open-mid back rounded vowel {{IPA|[ɔ]}} or an open back rounded vowel {{IPA|[ɒ]}}; in American English, it is most commonly an unrounded back {{IPA|[ɑ]}} to a central vowel {{IPA|[a]}}.{{Cite web |title=International Phonetic Alphabet for American English - IPA Chart |url=https://easypronunciation.com/en/american-english-pronunciation-ipa-chart |access-date=2024-01-03 |website=easypronunciation.com}}

Common digraphs include {{angbr|oo}}, which represents either {{IPAc-en|uː}} or {{IPAc-en|ʊ}}; {{angbr|oi}} or {{angbr|oy}}, which typically represents the diphthong {{IPAc-en|ɔɪ}}, and {{angbr|ao}}, {{angbr|oe}}, and {{angbr|ou}} which represent a variety of pronunciations depending on context and etymology.

In other contexts, especially before a letter with a minim, {{angbr|o}} may represent the sound {{IPAc-en|ʌ}}, as in 'son' or 'love'. It can also represent the semivowel {{IPAc-en|w}}, as in choir or quinoa.{{fact|date=November 2022}}

"O" in isolation is a word, also spelled "oh" and pronounced {{IPA|/oʊ/}}. Before a noun, usually capitalized, it indicates direct address (the vocative case), as in the titles "O Canada" or "O Captain! My Captain!" or in certain verses of the Bible.{{cite web|url=http://www.biblegateway.com/quicksearch/?quicksearch=%22o+lord%22&qs_version=KJV |title=Quick search: "o lord" |access-date=2013-12-05}}

{{angbr|o}} is commonly associated with the open-mid back rounded vowel {{IPA|[ɔ]}}, mid back rounded vowel {{IPA|[o̞]}} or close-mid back rounded vowel {{IPA|[o]}} in many languages. Other languages use {{angbr|o}} for various values, usually back vowels which are at least partly open. Derived letters such as {{angbr|ö}} and {{angbr|ø}} have been created for the alphabets of some languages to distinguish values that were not present in Latin and Greek, particularly rounded front vowels.{{fact|date=November 2022}}

In the International Phonetic Alphabet, {{angbr IPA|o}} represents the close-mid back rounded vowel.{{Cite web |title=IPA Chart with Sounds – International Phonetic Alphabet Sounds |url=https://www.internationalphoneticalphabet.org/ipa-sounds/ipa-chart-with-sounds/ |access-date=2023-10-22 |website=www.internationalphoneticalphabet.org}}

{{main article|O (disambiguation)}}

• Oxygen, symbol O, a chemical element

{{see also|Circle symbol (disambiguation){{!}}circle symbol}}

{{Flowlist|

• Œ œ : Latin OE ligature
• O with diacritics: Ø ø Ǿ ǿ Ö ö Ȫ ȫ Ó ó Ò ò Ô ô Ố ố Ồ ồ Ổ ổ Ỗ ỗ Ộ ộ Ǒ ǒ Ő ő Ŏ ŏ Ȏ ȏ Ȯ ȯ Ȱ ȱ Ọ ọ Ɵ ɵ ᶱ{{cite web|url=https://www.unicode.org/L2/L2004/04132-n2740-phonetic.pdf|title=L2/04-132 Proposal to add additional phonetic characters to the UCS|date=2004-04-19|first=Peter|last=Constable}} Ơ ơ Ớ ớ Ờ ờ Ỡ ỡ Ợ ợ Ở ở Ỏ ỏ Ō ō Ṓ ṓ Ṑ ṑ Õ õ Ȭ ȭ Ṍ ṍ Ṏ ṏ Ǫ ǫ Ȍ ȍ O̩ o̩ Ó̩ ó̩ Ò̩ ò̩ Ǭ ǭ O͍ o͍
• Ꝍ ꝍ : O with loop was used in some medieval Nordic orthographies{{cite web|url=https://www.unicode.org/L2/L2006/06027-n3027-medieval.pdf|title=L2/06-027: Proposal to add Medievalist characters to the UCS|date=2006-01-30|first1=Michael|last1=Everson|first2=Peter|last2=Baker|first3=António|last3=Emiliano|first4=Florian|last4=Grammel|first5=Odd Einar|last5=Haugen|first6=Diana|last6=Luft|first7=Susana|last7=Pedro|first8=Gerd|last8=Schumacher|first9=Andreas|last9=Stötzner}}
• Ꟁ ꟁ : Old Polish O{{Cite web|title=L2/21-039: Proposal to include the letter 'Old Polish O'|url=https://www.unicode.org/L2/L2021/21039-old-polish-o.pdf|date=2021-01-12|first=Daniel|last=Bunčić}}
• ⱺ : Small o with low ring inside is used in the Swedish Dialect Alphabet{{cite web|url=https://www.unicode.org/L2/L2006/06036-lma-proposal.pdf|title=L2/06-036: Proposal to encode characters for Ordbok över Finlands svenska folkmål in the UCS|date=2006-01-26|first1=Therese|last1=Lemonen|first2=Klaas|last2=Ruppel|first3=Erkki I.|last3=Kolehmainen|first4=Caroline|last4=Sandström}}
• IPA-specific symbols related to O: {{IPA link|ɔ}}
• IPA superscript letters:{{Cite web|title=L2/20-252R: Unicode request for IPA modifier-letters (a), pulmonic|url=https://www.unicode.org/L2/L2020/20252r-mod-ipa-a.pdf|date=2020-11-08|first1=Kirk|last1=Miller|first2=Michael|last2=Ashby}} 𐞢 𐞣
• Uralic Phonetic Alphabet-specific symbols related to O:{{cite web|url=https://www.unicode.org/L2/L2002/02141-n2419-uralic-phonetic.pdf|title=L2/02-141: Uralic Phonetic Alphabet characters for the UCS|date=2002-03-20|first1=Michael|last1=Everson|author-link1=Michael Everson|display-authors=etal}}
• {{Unichar|1D0F|LATIN LETTER SMALL CAPITAL O}}
• {{Unichar|1D3C|MODIFIER LETTER CAPITAL O}}
• {{Unichar|1D52|MODIFIER LETTER SMALL O}}
• {{Unichar|1D11|LATIN SMALL LETTER SIDEWAYS O}}
• {{Unichar|1D13|LATIN SMALL LETTER SIDEWAYS O WITH STROKE}}
• {{Unichar|1D16|LATIN SMALL LETTER TOP HALF O}}
• {{Unichar|1D17|LATIN SMALL LETTER BOTTOM HALF O}}
• {{Unichar|1D54|MODIFIER LETTER SMALL TOP HALF O}}
• {{Unichar|1D55|MODIFIER LETTER SMALL BOTTOM HALF O}}
• Teuthonista phonetic transcription-specific symbols related to O:{{cite web|url=https://www.unicode.org/L2/L2011/11202-n4081-teuthonista.pdf|title=L2/11-202: Revised proposal to encode "Teuthonista" phonetic characters in the UCS|date=2011-06-02|first1=Michael|last1=Everson|first2=Alois|last2=Dicklberger|first3=Karl|last3=Pentzlin|first4=Eveline|last4=Wandl-Vogt}}
• {{Unichar|AB3D|LATIN SMALL LETTER BLACKLETTER O}}
• {{Unichar|AB3E|LATIN SMALL LETTER BLACKLETTER O WITH STROKE}}
• {{Unichar|AB3F|LATIN SMALL LETTER OPEN O WITH STROKE}}
• {{Unichar|AB43|LATIN SMALL LETTER TURNED O OPEN-O}}
• {{Unichar|AB44|LATIN SMALL LETTER TURNED O OPEN-O WITH STROKE}}
• _o : Subscript small o is used in Indo-European studies{{cite web|url=https://www.unicode.org/L2/L2004/04191-n2788-laryngeals.pdf|title=L2/04-191: Proposal to encode six Indo-Europeanist phonetic characters in the UCS|date=2004-06-07|first1=Deborah|last1=Anderson|first2=Michael|last2=Everson}}
• 𝼛 : Latin small letter o with retroflex hook is used in phonetic transcription{{Cite web|title=L2/20-125R: Unicode request for expected IPA retroflex letters and similar letters with hooks|url=https://www.unicode.org/L2/L2020/20125r-ipa-retroflex.pdf|date=2020-07-11|first=Kirk|last=Miller}}{{Cite web|title=L2/21-021: Reference doc numbers for L2/20-266R "Consolidated code chart of proposed phonetic characters" and IPA etc. code point and name changes|url=https://www.unicode.org/L2/L2021/21021-consolidated-ipa.pdf|date=2020-12-07|first=Deborah|last=Anderson}}

}}

• Ꝋ ꝋ : Forms of O were used for medieval scribal abbreviations
• ∅ : empty set symbol{{cite web|url=https://jeff560.tripod.com/set.html|title=Earliest Uses of Symbols of Set Theory and Logic|website=jeff560.tripod.com}}
• º : Masculine ordinal indicator
• Calligraphic O (𝒪, 𝓸): Mathematical Alphanumeric Symbols{{Cite web |title=Script (or Calligraphic) |url=https://www.w3.org/TR/xml-entity-names/script.html |access-date=2024-01-03 |website=www.w3.org}}

• 𐤏 : Semitic letter Ayin, from which the following symbols originally derive:
• Ω ω : Greek letter Omega
• Ο ο : Greek letter Omicron
• {{Script|Copt|Ⲟ ⲟ}} : Coptic letter O, which derives from Greek omicron
• О о : Cyrillic letter O, which also derives from Omicron
• 𐌏 : Old Italic O, which derives from Greek Omicron, and is the ancestor of modern Latin O
• Օ օ : Armenian letter O{{citation needed|date=October 2015}}

{{anchor|Codes for computing}}

{{charmap

| 004F | name1 = LATIN CAPITAL LETTER O

| 006F| name2 = LATIN SMALL LETTER O

| FF2F | name3 = FULLWIDTH LATIN CAPITAL LETTER O

| FF4F | name4 = FULLWIDTH LATIN SMALL LETTER O

| ifr| map1 = EBCDIC family | map1char1 = D6 | map1char2 = 96

| map2 = ASCII{{efn|Also for encodings based on ASCII, including the DOS, Windows, ISO-8859 and Macintosh families of encodings.{{fact|date=November 2022}}}} | map2char1 = 4F | map2char2 = 6F

}}

{{Letter other reps

|NATO=Oscar

|Morse=–––

|Character=O

|Braille=⠕

|fingerspelling=O

}}

{{clear}}

• O mark
• Open O (Ɔ ɔ)
• 0 (zero). The capital letter O may be mistaken or misused for the number 0, as they appear quite identical in some typefaces. Early typewriters did not have a 'zero' key.

{{Notelist}}

{{Reflist}}

{{Wiktionary|O|o}}

• {{Commons category-inline|O}}

{{Latin alphabet|O|}}

Category:ISO basic Latin letters

Category:Vowel letters