| Mark: | ÷ † ⁒ ⸓ |
| Modern forms of the obelus | |
| Unicode: | |
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:
The word "obelus" comes from (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.
See also: Obelism. 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.
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,[9] 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.[10] 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 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,
⋅ / ⋅
In the 7.0 release of Unicode, was one of a group of "Ancient Greek textual symbols" that were added to the specification (in the block Supplemental Punctuation).[15]
See main article: Division sign.
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.[16] [17] 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.[18]
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).[19] In Italy, Poland and Russia, this notation is sometimes used in engineering to denote a range of values.[20]
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.[21] [22]