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An obelus (plural: obeluses or obeli) is a term in codicology and latterly in typography that refers to a historical annotation mark which has resolved to three modern meanings:
- Division sign ÷
- Dagger †
- Commercial minus sign ⁒ (limited geographical area of use)
| ÷ † ⁒ ⸓ | |
|---|---|
Modern forms of the obelus | |
| In Unicode | U+00F7 ÷ DIVISION SIGN U+2020 † DAGGER U+2052 ⁒ COMMERCIAL MINUS SIGN U+2E13 ⸓ DOTTED OBELOS |
| Different from | |
| Different from | U+0025 % PERCENT SIGN |
| Related | |
| See also | U+261E ☞ WHITE RIGHT POINTING INDEX |
The word "obelus" comes from ὀβελός (obelós), the Ancient Greek word for a sharpened stick, spit, or pointed pillar.[1] This is the same root as that of the word 'obelisk'.[2]
In mathematics, the first symbol is mainly used in Anglophone countries to represent the mathematical operation of division and is called an obelus.[3] In editing texts, the second symbol, also called a dagger mark † is used to indicate erroneous or dubious content;[4][5] or as a reference mark or footnote indicator.[6] It also has other uses in a variety of specialist contexts.
Use in text annotation
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Perspective
The modern dagger symbol originated from a variant of the obelus, originally depicted by a plain line −, or a line with one or two dots ⨪ ÷.[7] It represented an iron roasting spit, a dart, or the sharp end of a javelin,[8] symbolizing the skewering or cutting out of dubious matter.[9]
Originally, one of these marks (or a plain line) was used in ancient manuscripts to mark passages that were suspected of being corrupted or spurious; the practice of adding such marginal notes became known as obelism. The dagger symbol †, also called an obelisk,[10] is derived from the obelus, and continues to be used for this purpose.
The obelus is believed to have been invented by the Homeric scholar Zenodotus, as one of a system of editorial symbols. They marked questionable or corrupt words or passages in manuscripts of the Homeric epics.[9] The system was further refined by his student Aristophanes of Byzantium, who first introduced the asterisk and used a symbol resembling a ⊤ for an obelus; and finally by Aristophanes' student, in turn, Aristarchus, from whom they earned the name of "Aristarchian symbols".[11][12]
In some commercial and financial documents, especially in Germany and Scandinavia, a variant (U+2052 ⁒ COMMERCIAL MINUS SIGN) is used in the margins of letters to indicate an enclosure, where the upper point is sometimes replaced with the corresponding number.[13] In Finland, the obelus (or a slight variant, ) is used as a symbol for a correct response (alongside the check mark, ✓, which is used for an incorrect response).[14][15]
In the 7.0 release of Unicode, U+2E13 ⸓ DOTTED OBELOS was one of a group of "Ancient Greek textual symbols" that were added to the specification (in the block Supplemental Punctuation).[16]
In mathematics
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Perspective
The form of the obelus as a horizontal line with a dot above and a dot below, ÷, was first used as a symbol for division by the Swiss mathematician Johann Rahn in his book Teutsche Algebra in 1659. This gave rise to the modern mathematical symbol ÷, used in anglophone countries as a division sign.[17][18] This usage, though widespread in Anglophone countries, is neither universal nor recommended: the ISO 80000-2 standard for mathematical notation recommends only the solidus / or fraction bar for division, or the colon : for ratios; it says that ÷ "should not be used" for division.[19] The ambiguity of mathematical expressions that involve the obelus and implicit multiplication has become a subject of Internet memes.
This form of the obelus was also occasionally used as a mathematical symbol for subtraction in Northern Europe; such usage continued in some parts of Europe (including Norway and, until fairly recently, Denmark).[20] In Italy, Poland and Russia, this notation is sometimes used in engineering to denote a range of values.[21]
In some commercial and financial documents, especially in Germany and Scandinavia, another form of the obelus – the commercial minus sign – is used to signify a negative remainder of a division operation.[22][14]
See also
- Manicule – Symbol depicting a pointing finger ( ☞ ) used for obelism.
- Obelisk – Tall, four-sided, narrow tapering monument which ends in a pyramid-like shape at the top
- Obelix – Cartoon character in the French comic book series Asterix
- Obol (coin) – Unit of ancient Greek coinage
- List of typographical symbols and punctuation marks
References
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