The name of this letter is the same as the sound it represents (see
usage). Among English-speaking typographers the symbol may be called a "slashed O"[1] or "o with stroke". Although these names suggest it is a
ligature or a
diacritical variant of the letter ⟨o⟩, it is considered a separate letter in Danish and Norwegian, and it is alphabetized after ⟨z⟩ — thus ⟨x⟩, ⟨y⟩, ⟨z⟩, ⟨
æ⟩, ⟨ø⟩, and ⟨
å⟩.
In other languages that do not have the letter as part of the regular alphabet, or in limited
character sets such as
ASCII, ⟨ø⟩ may correctly be replaced with the
digraph⟨oe⟩, although in practice it is often replaced with just ⟨o⟩, e.g. in
email addresses. It is equivalent to ⟨
ö⟩ used in Swedish (and a number of other languages), and may also be replaced with ⟨ö⟩, as was often the case with older typewriters in
Denmark and
Norway, and in national extensions of
International Morse Code.
In modern
Danish,
Faroese, and
Norwegian, the letter is a
monophthongalclose-mid front rounded vowel, the
IPA symbol for which is also [ø] (
Unicode U+00F8). As with so many vowels, it has slight variations of "light" quality (in Danish, søster ("sister") is pronounced as [ø], like the "eu" in the French word bleu) and "dark" quality (in Danish, bønne ("bean") is pronounced as [œ], like the "œu" in the French word bœuf).[2]Listen to a Danish speaker reciting the Danish alphabet. In the
Suðuroy-dialect of Faroese, the short ø is pronounced [ʏ], e.g. børn[bʏdn] ("children"). The letter was used in both
Antiqua and
Fraktur from at least as early as the
Christian 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
Helsingör or
Læsö) until 1957.[3]
The
Southern Sami language uses the letter ø in Norway. It is used in the diphthongs yø[yo] and øø[oe]. In Sweden, the letter
ö is preferred.
The
Iaai language uses the letter ø to represent the sound [ø].
Ǿ (Ø with an
acute accent,
Unicode U+01FE) may be used in
Danish on rare occasions to distinguish its use from a similar word with Ø. Example: hunden gǿr, "the dog barks" against hunden gør (det), "the dog does (it)". This distinction is not mandatory and the first example can be written either gǿr or gør; the first variant (with ǿ) would only be used to avoid confusion. The second example cannot be spelled gǿr. In Danish, hunden gør, "the dog barks", may sometimes be replaced by the non-standard spelling hunden gøer. This is, however, usually based on a misunderstanding of the grammatic rules of
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
umlautso > ø and ǫ > ø.
In
Old Polish texts, the letter Ø represented a nasal vowel (after all nasal vowels had merged).
Outside Europe, Ø is used in Latin transliteration of the
Seneca language as the equivalent of the
ampersand; it abbreviates the Seneca word koh.
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".[4]
Ø / ø is not related to, and should not be confused with similar-looking
Greek Φ /
φ or
CyrillicФ / ф.
The
Cyrillic letter
Ө has the same sound as Ø, which is used in the Cyrillic alphabets for
Kazakh,
Mongolian,
Azerbaijani, and other languages that have this sound. This is not to be confused with the
Early Cyrillic letter
fita Ѳ.
The letter Ø-with-diæresis (Ø̈, ø̈) was used by the
Øresund bridge company, as part of their
logotype, 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 brand Snøre/Snöre's logo on the packaging is Snø̈re. The letter is rarely used on maps (e.g.: Grø̈nland).[5]
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
Bourbaki, and sometimes in linguistics as a replacement for same symbol used to represent a
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
typefaces 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 drawings, and it is also seen in situations where abbreviating "diameter" is useful, such as on
camera lenses. For example, a lens with a diameter of 82 millimeters would be engraved with " ⌀ 82 mm ".
Ø or
⌀ is sometimes also used as a symbol for
average value, particularly in German-speaking countries. ("Average" in German is Durchschnitt, directly translated as cut-through.)[6]
Slashed zero is an alternate
glyph for the
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
confounding of the two, particularly in
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,[7] for information on international amateur radio call signs.
The letter "Ø" is often used in
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 arose to represent an /ø/ sound resulting primarily from
i-mutation of /o/. There are at least two theories about the origin of the letter ø:[citation needed]
It possibly arose as a version of the
ligature,
Œ, of the
digraph "
oe", with the horizontal line of the "e" written across the "o".
It possibly arose in
Anglo-Saxon England as an O and an I written in the same place: compare
Bede's
Northumbrian Anglo-Saxon period spelling Coinualch for standard Cēnwealh (a man's name) (in a text in
Latin). Later the letter ø disappeared from Anglo-Saxon as the Anglo-Saxon sound /ø/ changed to /e/, but by then use of the letter ø had spread from England to
Scandinavia.
In Unicode, Ǿ and ǿ have the code points U+01FE and U+01FF.
On
Microsoft Windows, using the "United States-International" keyboard setting, it can be typed by holding down the
Alt-Gr key and pressing "L". It can also be typed under any keyboard setting by pressing NumLock, holding down the Alt key while typing 0216 (for uppercase) or 0248 (for lowercase) on the
numeric keypad, provided the system uses
code page 1252 as system default. (Code page 1252 is a superset of ISO 8859-1, and 216 and 248 are the decimal equivalents of
hexadecimal D8 and F8.)
In
macOS, it can be typed by holding O, or o, and then typing 6. In MacOS and earlier systems, using a US English-language keyboard, the letter can be typed by holding the
[Option] key while typing O, or o, to yield Ø, or ø.
In the
X Window System environment, one can produce these characters by pressing Alt-Gr and o or O, or by pressing the
Multi key followed with a slash and then o or O.
In some systems, such as older versions of
MS-DOS, the letter Ø is not part of the widely used
code page 437. In Scandinavian codepages, Ø replaces the
yen sign (¥) at 165, and ø replaces the
¢ sign at 162.
On an
Amiga operating system using any keyboard map, the letter can be typed by holding the
[Alt] key while typing O, or o, to yield Ø, or ø.