An interpunct, ·, also known as an interpoint, middle dot, middot and centered dot or centred dot, is a punctuation mark consisting of a vertically centered dot used for interword separation in ancient Latin script. (Word-separating spaces did not appear until some time between 600 and 800 CE). It appears in a variety of uses in some modern languages and is present in Unicode as U+00B7 · MIDDLE DOT.
The multiplication dot (Unicode U+22C5 ⋅ DOT OPERATOR) is frequently used in mathematical and scientific notation, it may differ in appearance from the interpunct.
Various dictionaries use the interpunct (in this context, sometimes called a hyphenation point) to indicate where to split a word and insert a hyphen if the word doesn't fit on the line. There is also a separate Unicode character, U+2027 ‧ HYPHENATION POINT.
In British typography, the space dot is an interpunct used as the formal decimal point. Its use is advocated by laws and in some academic circles such as the Cambridge University History Faculty Style Guide and is mandated by some UK-based academic journals such as The Lancet. When the British currency was decimalised in 1971, the official advice issued was to write decimal amounts with a raised point (for example, £21·48) and to use a decimal point "on the line" only when typesetting constraints made it unavoidable. This usage has been declining since the mid-1970s because the standard UK keyboard layout (for typewriters and computers) has only the full stop. The space dot is still used by some in handwriting.
In the early modern era, full stops (periods) were sometimes written as interpuncts (for example in the handwritten Mayflower Compact).
The punt volat ("flying point") is used in Catalan between two Ls in cases where each belongs to a separate syllable, for example cel·la, "cell". This distinguishes such "geminate Ls" (ela geminada), which are pronounced [ɫː], from "double L" (doble ela), which are written without the flying point and are pronounced [ʎ]. In situations where the flying point is unavailable, periods (as in col.lecció) or hyphens (as in col-lecció) are frequently used as substitutes, but this is tolerated rather than encouraged.
There is no separate keyboard layout for Catalan: the flying point can be typed using ⇧ Shift+3 in the Spanish (Spain) layout. It appears in Unicode as the pre-composed letters Ŀ (U+013F) and ŀ (U+0140), but they are compatibility characters and are not frequently used or recommended.[a]
The interpunct is used in Chinese (which generally lacks spacing between characters) to mark divisions in transliterated foreign words, particularly names. This is properly (and in Taiwan formally) a full-width partition sign (Unicode code point U+2027, Hyphenation Point), although sometimes narrower forms are substituted for aesthetic reasons. In particular, the regular interpunct is more commonly used as a computer input, although Chinese-language fonts typically render this as full width. When the Chinese text is romanized, the partition sign is simply replaced by a standard space or other appropriate punctuation. Thus, William Shakespeare is signified as 威廉·莎士比亞 or 威廉·莎士比亞 (p Wēilián Shāshìbǐyà), George W. Bush as 喬治·W·布殊 or 喬治·W·布什 (p Qiáozhì W. Bùshí) and the full name of the prophet Muhammad as 阿布·卡西木·穆罕默德·本·阿布杜拉·本·阿布杜勒-穆塔利卜·本·哈希姆 (p Ābù Kǎxīmù Mùhǎnmòdé Běn Ābùdùlā Běn Ābùdùlè-Mùtǎlìbǔ Běn Hāxīmǔ). Titles and other translated words are not similarly marked: Genghis Khan and Elizabeth II are simply 成吉思汗 and 伊利沙伯二世 or 伊麗莎白二世 without a partition sign.
The partition sign is also used to separate book and chapter titles when they are mentioned consecutively: book first and then chapter.
In Pe̍h-ōe-jī for Taiwanese Hokkien, middle dot is often used as a workaround for dot above right diacritic because most early encoding systems did not support this diacritic. This is now encoded as U+0358 ͘ COMBINING DOT ABOVE RIGHT (see o͘). Unicode did not support this diacritic until June 2004. Newer fonts often support it natively; however, the practice of using middle dot still exists. Historically, it was derived in the late 19th century from an older barred-o with curly tail as an adaptation to the typewriter.
The Geʽez (Ethiopic) script traditionally separates words with an interpunct of two vertically aligned dots, like a colon, but with larger dots: ፡ (U+1361). (For example ገድለ፡ወለተ፡ጴጥሮስ). Starting in the late 19th century the use of such punctuation has largely fallen out of use in favor of whitespace, except in formal hand-written or liturgical texts. In Eritrea the character may be used as a comma.
In Franco-Provençal (or Arpitan), the interpunct is used in order to distinguish the following graphemes:
The modern Greek ano teleia mark (άνω τελεία, ánō teleía, lit. "upper stop"), also known as the áno stigmī́ (άνω στιγμή), is the infrequently-encountered Greek semicolon and is properly romanized as such. It is also used to introduce lists in the manner of an English colon. In Greek text, Unicode provides a unique code point— U+0387 · GREEK ANO TELEIA—but it is also expressed as an interpunct. In practice, the separate code point for ano teleia canonically decomposes to the interpunct.
Interpuncts are often used to separate transcribed foreign names or words written in katakana. For example, "Can't Buy Me Love" becomes 「キャント・バイ・ミー・ラヴ」 (Kyanto·bai·mī·rabu). A middle dot is also sometimes used to separate lists in Japanese instead of the Japanese comma ("、" known as tōten). Dictionaries and grammar lessons in Japanese sometimes also use a similar symbol to separate a verb suffix from its root. Note that while some fonts may render the Japanese 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.
The interpunct also has a number of other uses in Japanese, including the following: to separate titles, names and positions: 課長補佐・鈴木 (Assistant Section Head · Suzuki); as a decimal point when writing numbers in kanji: 三・一四一五九二 (3.141 592); as a slash when writing for "or" in abbreviations: 月・水・金曜日 (Mon/Wed/Friday); and in place of hyphens, dashes and colons when writing vertically.
Interpuncts are used in written Korean to denote a list of two or more words, more or less in the same way a slash (/) is used to juxtapose words in many other languages. In this role it also functions in a similar way to the English en dash, as in 미·소관계, "American–Soviet relations". The use of interpuncts has declined in years of digital typography and especially in place of slashes, but, in the strictest sense, a slash cannot replace a middle dot in Korean typography.
U+318D ㆍ HANGUL LETTER ARAEA (아래아) is used more than a middle dot when an interpunct is to be used in Korean typography, though araea is technically not a punctuation symbol but actually an obsolete Hangul jamo. Because araea is a full-width letter, it looks better than middle dot between Hangul. In addition, it is drawn like the middle dot in Windows default Korean fonts such as Batang.
The interpunct (interpunctus) was regularly used in classical Latin to separate words. In addition to the most common round form, inscriptions sometimes use a small equilateral triangle for the interpunct, pointing either up or down. It may also appear as a mid-line comma, similar to the Greek practice of the time. The interpunct fell out of use c. 200 CE, and Latin was then written scripta continua for several centuries.
In Old Occitan, the symbol · was sometimes used to denote certain elisions, much like the modern apostrophe, the only difference being that the word that gets to be elided is always placed after the interpunct, the word before ending either in a vowel sound or the letter n:
In many linguistic works discussing Old Irish (but not in actual Old Irish manuscripts), the interpunct is used to separate a pretonic preverbal element from the stressed syllable of the verb, e.g. do·beir "gives". It is also used in citing the verb forms used after such preverbal elements (the prototonic forms), e.g. ·beir "carries", to distinguish them from forms used without preverbs, e.g. beirid "carries". In other works, the hyphen (do-beir (do- prefix), -beir) or colon (do:beir, :beir) may be used for this purpose.
Runic texts use either an interpunct-like or a colon-like punctuation mark to separate words. There are two Unicode characters dedicated for this: U+16EB ᛫ RUNIC SINGLE PUNCTUATION and U+16EC ᛬ RUNIC MULTIPLE PUNCTUATION.
Up to the middle of the 20th century, and sporadically even much later, the interpunct could be found used as the decimal marker in British publications, such as tables of constants (e.g., "π = 3·14159"). This made expressions such as 15 · 823 potentially ambiguous: does this denote 15 × 823 = 12345, or 15823/1000?.
In publications conforming to the standards of the International System of Units, next to the multiplication sign (×), the centered dot (dot operator) or space (often typographically a non-breaking space) can be used as a multiplication sign. Only a comma or full stop (period) may be used as a decimal marker. The centered dot can be used when multiplying units, as in m · kg · s−2 for the newton expressed in terms of SI base units. However, when the decimal point is used as the decimal marker, as in the US, the use of a centered dot for the multiplication of numbers or values of quantities is discouraged.
In mathematics, a small middle dot can be used to represent product; for example, x ∙ y for the product of x and y. When dealing with scalars, it is interchangeable with the multiplication sign, × such that x ⋅ y means the same thing as x × y. However, when dealing with vectors, the dot product is distinct from the cross product. For the scalar product of vectors, only the Dot Operator is used.
The bullet operator, ∙, U+2219, is sometimes used to denote the "AND" relationship in formal logic. Another usage of this symbol is in functions, denoting a parameter, which varies, for example, θ(s,a,·). In situations where the interpunct is used as a decimal point, the multiplication sign used is usually a full stop (period), not an interpunct.
In computing, the middle dot is usually displayed (but not printed) to indicate white space in various software applications such as word processing, graphic design, web layout, desktop publishing or software development programs. In some word processors, interpuncts are used to denote not only hard space or space characters, but also sometimes used to indicate a space when put in paragraph format to show indentations and spaces. This allows the user to see where white space is located in the document and what sizes of white space are used, since normally white space is invisible so tabs, spaces, non-breaking spaces and such are indistinguishable from one another.
A middot may be used as a consonant or modifier letter, rather than as punctuation, in transcription systems and in language orthographies. For such uses Unicode provides the code point U+A78F ꞏ LATIN LETTER SINOLOGICAL DOT.
In the Sinological tradition of the 36 initials, the onset 影 (typically reconstructed as a glottal stop) may be transliterated with a middot ⟨ꞏ⟩, and the onset 喩 (typically reconstructed as a null onset) with an apostrophe ⟨ʼ⟩. Conventions vary, however, and it is common for 影 to be transliterated with the apostrophe. These conventions are used both for Chinese itself and for other scripts of China, such as ʼPhags-pa and Jurchen.
In Americanist phonetic notation, the middot is a more common variant of the colon ⟨꞉⟩ used to indicate vowel length. It may be called a half-colon in such usage. Graphically, it may be high in the letter space (the top dot of the colon) or centered as the interpunct. From Americanist notation, it has been adopted into the orthographies of several languages, such as Washo.
In the Canadian Aboriginal Syllabics, a middle dot ⟨ᐧ⟩ indicates a syllable medial ⟨w⟩ in Cree and Ojibwe, ⟨y⟩ or ⟨yu⟩ in some of the Athapascan languages, and a syllable medial ⟨s⟩ in Blackfoot. However, depending on the writing tradition, the middle dot may appear after the syllable it modifies (which is found in the Western style) or before the syllable it modifies (which is found in the Northern and Eastern styles). In Unicode, the middle dot is encoded both as independent glyph U+1427 ᐧ CANADIAN SYLLABICS FINAL MIDDLE DOT or as part of a pre-composed letter, such as in U+143C ᐼ CANADIAN SYLLABICS PWI. In the Carrier syllabics subset, the middle dot Final indicates a glottal stop, but a centered dot diacritic on [ə]-position letters transform the vowel value to [i], for example: U+1650 ᙐ CANADIAN SYLLABICS CARRIER SE, U+1652 ᙒ CANADIAN SYLLABICS CARRIER SI.
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