Interpunct

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An interpunct is a small dot used for interword separation in ancient Latin script, being perhaps the first consistent visual representation of word boundaries in written language. The dot is vertically centered, e.g. "DONA·NOBIS·REQVIEM", and is therefore also called a middle dot or centered dot. In addition to the round dot form, inscriptions sometimes use a small equilateral triangle for the interpunct, pointing either up or down. Such triangles can be found on inscriptions on buildings in the twentieth century. Ancient Greek, by contrast, had not developed interpuncts; all the letters ran together. When a wave of enthusiasm for all things Greek swept ancient Rome, the use of interpuncts disappeared, presumably being inadequately fashionable. The use of spaces for word separation didn't appear until much later, some time between 600 and 800 AD.

In Unicode, the interpunct is code point 0183, or 00B7 in hexadecimal. The HTML entity for an interpunct is ·. See also "Similar symbols", below.

In written language

English

In British typography, an interpunct is sometimes called a space dot.

In some word processors, interpuncts are used to denote either hard space or space characters.

Latin

The dot called interpunct was used regularly in early Latin, but has long been replaced by space.

Georgian language

The Georgian language uses · (middot) as a comma.

Taiwanese

The Taiwanese dot above right (indicating a more open vowel) is often expressed as a Unicode middle dot, as the necessary combining character was not codified prior to June 2004; historically, it was derived in the late 19th century from an older barred-o with curly tail as an adaptation to the typewriter.

Chinese

The Chinese language sometimes uses the interpunct (called the partition sign) to separate words; since Chinese script has no word spacing, the interpunct is used in cases which might otherwise be ambiguous. The partition sign is more frequently used to separate the given name and the family name of non-Chinese, or unsinicized or desinicized minority ethnic groups in China, for example, 威廉·莎士比亞 (Weilian·Shashibiya) is the transliteration of "William Shakespeare", and the partition sign is inserted in between the characters signifying the sound of "William" and those for "Shakespeare". The Chinese partition sign is also used to separate book title and chapter title when they are mentioned consecutively (with book title first, then chapter).

In Chinese, the middle dot is also fullwidth in printed matter, but the regular middle dot (·) is used in computer input, which is then rendered as fullwidth in Chinese-language fonts. Note that while some fonts may render the Japanese katakana middle dot as a square under great magnification, this is not a defining property of the middle dot that is used in China or Japan.

Bernhard Karlgren used a middle dot to represent the glottal stop in his reconstruction of medieval Chinese.

Greek

The Greek Ano Teleia (a semicolon-like punctuation mark, lit. "upper dot") is often expressed as a middle dot, although Unicode provides for a unique U+0387. [1]

Japanese

Interpuncts are often used to separate transcribed foreign words written in Katakana. For example, "Can't Buy Me Love" becomes 「キャント・バイ・ミー・ラヴ」 ("Kyanto·bai·mii·ravu"). A middle dot is also sometimes used to separate lists in Japanese instead of the Japanese comma ("、" known as tōten). Grammar lessons in Japanese sometimes also use a similar symbol to separate a verb suffix from its root.

However, the Japanese writing system usually does not use space or punctuations to separate words; instead, the mixture of katakana, kanji, and hiragana gives some indication of word boundary.

In Japanese typography, the "katakana middle dot" (as the Unicode consortium calls it) has a fixed width that is the same as most kana characters, known as fullwidth.

Catalan

In Catalan, the punt volat (literally, "flown dot") is used between two l's (thus: l·l) in cases where each belongs to a separate syllable (e.g. col·lecció, collection). This is to distinguish the true "double-l" pronunciation from that of the letter-combination ll (without a dot) which in Catalan stands for the single sound represented by the IPA symbol [λ] (e.g. castellà, Castilian) . In spelling, l·l is called ela geminada ("geminate l") and ll doble ela. Where a middle dot is unavailable, a period is frequently used: col.lecció. Unicode has unique code points for the letters Ŀ (U+013F) and ŀ (U+0140), but they are not frequently used. Also, in Medieval Catalan the symbol was sometimes used to note certain ellisions, much like the modern apostrophe.

Shavian

In the Shavian alphabet, the middle dot is used before a word to denote it as a proper noun.

Runes

Runic texts use a semicolon-like punctuation mark to separate words.

In mathematics and science

In British publications up to the mid-1970s, especially scientific and mathematical texts, the decimal point was commonly typeset as a middle dot. When the British currency was decimalised in 1971, the official advice issued was to write decimal amounts with a raised point (thus: £21·48) and to use a decimal point "on the line" only when typesetting constraints made it unavoidable. The widespread introduction of electronic typewriters and calculators soon afterwards was probably a major factor contributing to the decline of the raised decimal point, although it can still sometimes be encountered in academic circles (e.g., Cambridge University 2004) and is fairly commonly used by mathematics teachers in schools.

In mathematics, a small middle dot can be used to represent the product; for example, x ∙ y for the product of x and y. When dealing with scalars, it is interchangeable with the times symbol: x ⋅ y means the same thing as x × y. However, when dealing with vectors, the dot product is distinct from the cross product. This usage has its own designated code point in Unicode, U+2219 (∙), called the "bullet operator". It is also sometimes used to denote the "AND" relationship in formal logic, due to the relationship between these two operations. In situations where the interpunct is used as a decimal point (as noted above, by many mathematics teachers in some countries), then the multiplication sign used is usually a full stop, not an interpunct.

In chemistry, the middle dot is used to separate the parts of formulas of addition compounds, mixture salts or solvates (mostly hydrates), such as of copper(II) sulfate pentahydrate, CuSO₄ · 5H₂O.

Similar symbols

Characters in the Symbol column, above, may not render correctly, if at all, in all browsers.

See also

• Punctuation