View source for Ø

{{about|the Scandinavian letter}}
{{distinguish|text=the Greek letter [[Phi]]; the Cyrillic letter [[Ef (Cyrillic)|Ef]]; or the number [[zero|0]], which is sometimes [[zero#Symbols and representations|written with a slash in the middle]]}}
{{Short description|Letter in several Latin-script alphabets}}
{{more citations needed|date=November 2015}}
{{Infobox grapheme
| type = [[Alphabet]]
| unicode = U+00D8, U+00F8
| name = O with slash
| associates = I, E
| variations = Öö, Ǿǿ, Ø̈ø̈
| language = Contested
| equivalents = OE oe, Öö, O/ o/
| letter = Øø
| script = [[Latin script]]
| phonemes = {{flex list|{{IPAblink|ø|audio=yes}}|{{IPAblink|œ|audio=yes}}|{{IPAblink|ʏ|audio=yes}}|[yo]|[oe]|}}
| image = Latin letter O with stroke.svg
| imageclass = skin-invert-image
| fam1 = <hiero>D4</hiero>
| fam2 = [[File:Proto-semiticO-01.svg|class=skin-invert-image|20px|Proto-sinaitic ʿayin]]
| fam3 = [[File:Protoayin.svg|class=skin-invert-image|20px]]
| fam4 = [[File:Phoenician ayin.svg|class=skin-invert-image|20px|Phoenician Ayin]]
| fam5 = [[Omicron|Ο ο]]
| fam6 = [[𐌏]]
| fam7 = [[O|O o]]
}}
'''Ø''' (or [[Lower case|minuscule]]: '''ø''') is a [[Letter (alphabet)|letter]] used in the [[Danish and Norwegian alphabet|Danish]], [[Danish and Norwegian alphabet|Norwegian]], [[Faroese language#Alphabet|Faroese]], and [[Southern Sámi language#Writing system|Southern Sámi]] languages. It is mostly used to represent the mid front rounded vowels, such as {{IPAblink|ø|audio=yes}} and {{IPAblink|œ|audio=yes}}, except for [[Southern Sámi]] where it is used as an {{IPA|[oe]}} [[diphthong]].

The name of this letter is the same as the sound it represents (see [[#Language usage|usage]]). Among English-speaking typographers the symbol may be called a "slashed O"<ref>{{cite book |last1=Pullum |first1=Geoffrey K. |first2=William A. |last2=Ladusaw |year=1996 |title=[[Phonetic Symbol Guide]] |edition=2nd |place=Chicago, IL |publisher=University of Chicago Press |page=136}}</ref> or "o with stroke". Although these names suggest it is a [[Ligature (writing)|ligature]] or a [[diacritic]]al variant of the letter {{vr|o}}, it is considered a separate letter in Danish and Norwegian, and it is alphabetized after {{vr|z}} — thus {{vr|x}}, {{vr|y}}, {{vr|z}}, {{vr|[[æ]]}}, {{vr|ø}}, and {{vr|[[å]]}}.

In other languages that do not have the letter as part of the regular alphabet, or in limited [[character set]]s such as [[ASCII]], {{vr|ø}} may correctly be replaced with the [[Digraph (orthography)|digraph]] {{vr|oe}}, although in practice it is often replaced with just {{vr|o}}, e.g. in [[email address]]es. It is equivalent to {{vr|[[ö]]}} used in Swedish (and a number of other languages), and may also be replaced with {{vr|ö}}, as was often the case with older typewriters in [[Denmark]] and [[Norway]], and in national extensions of [[International Morse Code]].{{cn|date=April 2025}}

{{vr|ø}} (minuscule) is also used in the [[International Phonetic Alphabet]] to represent a [[close-mid front rounded vowel]].

==Language usage==
=== Languages in Scandinavia ===
[[File:Bible of Christian III 1550.jpg|thumb|Title page of the [[Bible translations in Norway#Christian III's Bible and versions based on this|Christian&nbsp;III Bible]], employing the spelling "[[Copenhagen|Københaffn]]"]][[File:OwithStrokeandacute.png|class=skin-invert-image|thumb|O with Stroke and acute in [[Doulos SIL]]]]

* In modern [[Danish language|Danish]], [[Faroese language|Faroese]], and [[Norwegian language|Norwegian]], the letter generally represents [[close-mid front rounded vowel]], the [[International Phonetic Alphabet|IPA symbol]] for which is {{IPA|[ø]}} ([[Unicode]] U+00F8). As with so many vowels, it has slight variations in quality. Besides the close-mid vowel, as in Danish {{lang|da|søster}} ("sister") pronounced {{IPA|[ø]}}, like the {{vr|eu}} in the French word {{lang|fr|bleu}}), {{vr|ø}} may have a lower vowel quality, e.g. in Danish {{lang|da|bønne}} ("bean") pronounced {{IPA|[œ]}}, like the {{vr|œu}} in the French word {{lang|fr|bœuf}}).<ref>{{cite web |title=Introduction |series=Nordic FAQ |website=FAQs.org |url=http://www.faqs.org/faqs/nordic-faq/part1_INTRODUCTION/section-7.html}}</ref> In the [[Suðuroy]]-dialect of Faroese, the short {{vr|ø}} is pronounced {{IPA|[ʏ]}}, e.g. {{lang|fo|børn}} {{IPA|[bʏdn]}} ("children"). The letter was used in both [[Antiqua (typeface class)|Antiqua]] and [[Fraktur]] from at least as early as the [[Bible translations in Norway#Christian III's Bible and versions based on this|Christian&nbsp;III Bible]]. Under German influence, the letter [[ö]] appeared in older texts (particularly those using [[Fraktur]]) and was preferred for use on maps (e.g., for [[Helsingør|Helsingör]] or [[Læsø|Læsö]]) until 1957.<ref>{{cite web |website=Den Store Danske |url=http://www.denstoredanske.dk/Samfund,_jura_og_politik/Sprog/Ortografi/%C3%B8_%C3%98 |title=Ø, ø}}</ref>
* The [[Southern Sami language]] uses the letter {{vr|ø}} in Norway. It is used in the diphthongs {{vr|yø}} {{IPA|[yo]}} and {{vr|øø}} {{IPA|[oe]}}. In Sweden, the letter {{vr|[[ö]]}} is preferred.
* '''{{visible anchor|Ǿ}}''' (Ø with an [[acute accent]], [[Unicode]] U+01FE) may be used in [[Danish language|Danish]] on rare occasions to distinguish its use from a similar word with Ø. Example: {{lang|da|hunden gǿr}}, "the dog barks" against {{lang|da|hunden gør (det)}}, "the dog does (it)". This distinction is not mandatory and the first example can be written either {{lang|da|gǿr}} or {{lang|da|gør}}; the first variant (with ǿ) would only be used to avoid confusion. The second example cannot be spelled {{lang|da|gǿr}}. In Danish, {{lang|da|hunden gør}}, "the dog barks", may sometimes be replaced by the non-standard spelling {{lang|da|hunden gøer}}. This is, however, usually based on a misunderstanding of the grammatic rules of [[Grammatical conjugation|conjugation]] of verbs ending in the letters ø and [[å]]. These idiosyncratic spellings are not accepted in the official language standard. On Danish keyboards and typewriters, the acute accent may be typed above any vowel, by pressing the acute key before pressing the letter, but Ǿ is not implemented in the Microsoft Windows keyboard layout for Danish.
* Ø is used in [[Old Icelandic]] texts, when written with the standardized orthography, denoting, among other things the [[Umlaut (linguistics)|umlauts]] ''o > ø'' and ''ǫ > ø''.

=== Other languages ===
* The [[Iaai language]] uses the letter {{vr|ø}} to represent the sound {{IPA|[ø]}}.
* {{vr|Ø}} is used in the orthographies of several [[languages of Africa]], such as [[Lendu language|Lendu]], spoken in the [[Democratic Republic of the Congo]], and [[Nzime language|Koonzime]], spoken in [[Cameroon]].
* Outside Europe, {{vr|Ø}} is used in Latin transliteration of the [[Seneca language]] as the equivalent of the [[ampersand]]; it abbreviates the Seneca word {{lang|see|koh}}.
* {{vr|Ø}} is used in some alphabets for the indigenous Mexican [[Ocuiltec language|Tlahuica language]] (also known as Pjyɇkakjo or Ocuiltec), where it represents the [[open-mid back unrounded vowel]] {{IPAblink|ʌ}}.<ref>{{cite journal |first1=Martha |last1=Muntzel |first2=Aileen |last2=Martínez |title=El Alfabeto Práctico Pjyɇkakjo |url=https://revistas.unam.mx/index.php/eco/article/download/52051/46393 |access-date=3 November 2025 |journal=Estudios de Cultura Otopame |volume=9 |date=2014 |publisher=Universidad Nacional Autónoma de México Instituto de Investigaciones Antropológicas}}</ref>
* Ø (or more properly, the similar [[null sign]], ∅), is used in English as a short for "no" or "none", but this usage is discouraged in handwriting, since it may be mistaken as another number, especially "0".<ref>{{cite web|url=https://www.hopkinsmedicine.org/gynecology_obstetrics/education/medstudents/_docs/learning_mtls/abbrev-prohibited.pdf|title=Medical Abbreviation Policy (PME006), Appendix A, Prohibited Abbreviations for Handwritten Documentation|website=[[Johns Hopkins School of Medicine]]}} Updated: 11/20/03 Effective 3/3/04</ref>

==Similar letters==
* The [[Turkish alphabet|Turkish]], [[Azerbaijani alphabet|Azerbaijani]], [[Turkmen alphabet|Turkmen]], [[Tatar alphabet|Tatar]], [[Swedish alphabet|Swedish]], [[Icelandic orthography|Icelandic]], [[Rotuman language#Orthography|Rotuman]], [[German alphabet|German]], [[Finnish alphabet|Finnish]], [[Estonian alphabet|Estonian]], and [[Hungarian alphabet|Hungarian]] alphabets use the letter [[Ö]] instead of Ø. [[Hungarian orthography]] uses Ő for the same sound lengthened.
* Ø / ø is not related to, and should not be confused with similar-looking [[Greek alphabet|Greek]] Φ / [[φ]] or [[Cyrillic]] [[Ф]] / ф.
* The [[Cyrillic script|Cyrillic]] letter [[Oe (Cyrillic)|Ө]] has the same sound as Ø, which is used in the Cyrillic alphabets for [[Kazakh alphabet|Kazakh]], [[Mongolian Cyrillic alphabet|Mongolian]], [[Azerbaijani alphabet|Azerbaijani]], and other languages that have this sound. This is not to be confused with the [[Early Cyrillic alphabet|Early Cyrillic]] letter [[Fita|fita Ѳ]].
* The letter Ø-with-diæresis (Ø̈, ø̈) was used by the [[Oresund Bridge|Øresund bridge]] company, as part of their [[logo]]type, to symbolize its union between Sweden and Denmark. Since Ø-with-diæresis did not exist in computer fonts, it was not used in the text. The logotype now uses the spelling Øresundsbron, with Øresunds- being Danish and -bron being Swedish. The letter Ø-with-diæresis sometimes appears on packaging meant for the Scandinavian market so as to prevent printing the same word twice. For example, [[Liquorice (confectionery)|liquorice]] brand Snøre/Snöre's logo on the packaging is ''Snø̈re''. The letter is rarely used on maps (e.g.: Malmø̈).<ref>Die Erde: Haack Kleiner Atlas; VEB Hermann Haack geographisch-kartographische Anstalt, Gotha, 1982; p. 78</ref>
* In [[Old Polish]] texts, the letter Ꟁ / ꟁ, called "o rogate" (eng. "horned o"), represented a nasal vowel (after all nasal vowels had merged, but before they re-diverged in modern Polish). Due to limitations in printing technology, this letter has sometimes been rendered as {{char|ø}}, {{char|φ}}, or {{char|ϕ}}.

==Similar symbols==
* The letter "Ø" is sometimes used in mathematics as a replacement for the symbol "∅" (Unicode character U+2205), referring to the [[empty set]] as established by [[Nicolas Bourbaki|Bourbaki]], and sometimes in linguistics as a replacement for same symbol used to represent a [[Zero (linguistics)|zero]]. The "∅" symbol is always drawn as a slashed [[circle]], whereas in most typefaces the letter "Ø" is a slashed [[ellipse]].
* The [[diameter]] symbol ([[⌀]]) (Unicode character U+2300) is similar to the lowercase letter ø, and in some [[typeface]]s it even uses the same [[glyph]], although in many others the glyphs are subtly distinguishable (normally, the diameter symbol uses an exact circle and the letter ''o'' is somewhat stylized). The diameter symbol is used extensively in [[engineering drawing]]s, and it is also seen in situations where abbreviating "diameter" is useful, such as on [[camera lens]]es. For example, a lens with a diameter of 82 millimeters would be engraved with {{nowrap|" ⌀ 82 mm ".}}
* Ø or [[⌀]] is sometimes also used as a symbol for [[average]] value, particularly in German-speaking countries. ("Average" in German is ''[[:wikt:Durchschnitt|Durchschnitt]]'', directly translated as ''cut-through''.)<ref>
{{cite web
 | last1=Beeton  |first1 = Barbara
 | last2=Freytag |first2 = Asmus 
 | last3=Iancu   |first3 = Laurențiu
 | last4=Sargent |first4 = Murray III
 |date = 30 October 2015
 |title = Proposal to Represent the Slashed Zero Variant of Empty Set
 |page = 6
 |website = The Unicode Consortium 
 |url = https://www.unicode.org/L2/L2015/15268-slashed-zero.pdf
}}
</ref>
* [[Slashed zero]] is an alternate [[glyph]] for the [[0 (number)|zero]] character. Its slash does not extend outside the ellipse (except in handwriting). It is often used to distinguish "zero" ("0") from the [[Latin script]] letter "O" anywhere that people wish to preempt [[wikt:confound#Verb|confounding]] of the two, particularly in [[code|encoding systems]], scientific and engineering applications, [[computer programming]] (such as [[software development]]), and telecommunications. It is also used in Amateur Radio call signs, such as XXØXX, XØXXX, and so on, in the United States and in other countries. See, also,<ref>
{{cite web
 |title = ITU Table of Allocation of International Call Sign Series
 |place = Newington, CT
 |publisher = [[American Radio Relay League]]
 |website = arrl.org
 |url = http://www.arrl.org/international-call-sign-series
}}
</ref> for information on international amateur radio call signs.
* The letter "Ø" is often used in [[Trapped-key interlocking|trapped-key interlock]] sequence drawings to denote a key trapped in a lock. A lock without a key is shown as an "O".
* The letter "Ø" is also used in written music, especially [[jazz]], to type an ad-hoc [[chord letter|chord symbol]] for a [[Half diminished seventh chord|half-diminished chord]], as in "Cø". The [[typography|typographically]] correct chord symbol is spelled with the [[Root (chord)|root name]], followed by a slashed [[degree symbol]], as in "C𝆩". The slashed degree symbol is found in the [[Musical Symbols (Unicode block)|musical symbols]] block of [[Unicode]] but is unsupported by some fonts.
* The [[null sign]], ∅

==History==
The letter arose as a version of the [[ligature (typography)|ligature]] {{vr|[[Oe (digraph)|oe]]}}. In Danish manuscripts from the 12th and 13th century, the letter used to represent an {{IPA|/ø/}} sound is most frequently written as an {{vr|o}} with a line through, but also {{vr|oe}}. The line could both be horizontal or vertical.<ref>{{cite journal |last1=Sandersen |first1=Vibeke |title=Om bogstavet ''ø'' |journal=Nyt fra Sprognævnet |date=2000 |issue=3 |pages=11–15 |url=https://dsn.dk/nyt/nyt-fra-sprognaevnet/numre/argang-2000-2004/september-2000-pdf#page=10 |access-date=13 June 2024}}</ref>

==Unicode==
[[File:Illuminated keyboard 2.JPG|thumb|right|Danish keyboard with keys for Æ, Ø, and Å. On Norwegian keyboards the [[Æ]] and Ø switch places.]]

Some 7-bit ASCII variants defined by [[ISO/IEC 646]] use {{tt|0x5C}} for Ø and {{tt|0x7C}} for ø, replacing the backslash and vertical bar.
The most common locations in [[EBCDIC]] code pages is {{tt|0x80}} and {{tt|0x70}}.
Most code pages used by [[MS-DOS]] such as [[CP437]] did not contain this character; in Scandinavian codepages, Ø replaces the [[¥|yen sign (¥)]] at 165, and ø replaces the [[Cent (currency)|¢]] sign at 162.
The 8-bit [[ISO-8859-1]] and similar sets used {{tt|0xD8}} and {{tt|0xF8}}; these locations were then inherited by [[CP1252]] on Windows, and by [[Unicode]].

* {{unichar|00D8|LATIN CAPITAL LETTER O WITH STROKE|html=}}
* {{unichar|00F8|LATIN SMALL LETTER O WITH STROKE|html=}}
Not to be confused with the mathematical signs:
* {{unichar|2205|EMPTY SET|html=}}
* {{unichar|2300|Diameter sign|html=}}

==See also==
* [[Æ]]
* [[Å]]
* [[Ä]]
* [[Œ]]
* [[Ö]]
* [[Slashed zero]]

==Notes==
{{reflist}}

==References==
* [[Robert Bringhurst]] (2002). ''[[The Elements of Typographic Style]]'', pp.&nbsp;270, 284. For typographic reference to "slashed o".

{{Latin script}}
{{Danish language}}
{{Norwegian language forms}}
{{Use dmy dates|date=September 2017}}

{{DEFAULTSORT:O, shlash}}
[[Category:Danish language]]
[[Category:Faroese language]]
[[Category:Norwegian language]]
[[Category:Phonetic transcription symbols]]
[[Category:Latin-script letters]]
[[Category:Vowel letters|Oe]]
[[Category:Polish letters with diacritics]]