Speaking Of Division
Outside Of Bryce Canyon National Park
November 6, 2020
Something to break out next time you want to bore someone. 🤪
The division sign ÷ is a symbol consisting of a short horizontal line with a dot above and another dot below, used to indicate mathematical division. However, this usage, though widespread in Anglophone countries, is not universal, and the symbol's use for division is not recommended in the ISO 80000-2 standard for mathematical notation.
The obelus, an historical glyph consisting of a horizontal line with (or without) one or more dots, was first used as a symbol for division in 1659, in the algebra book Teutsche Algebra by Johann Rahn. Some think that John Pell, who edited the book, may have been responsible for this use of the symbol. Other symbols for division include the slash or solidus /, the colon :, and the fraction bar (the horizontal bar in a vertical fraction). 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 the ÷ sign "should not be used" for division.
In Italy and Russia, the ÷ sign is sometimes used in engineering to denote a range of values.
Historically, an oblique form of the obelus, ⁒ (commercial minus sign), has also been used to represent subtraction in Northern Europe; such usage continued in some parts of Europe, including Norway and—until fairly recently—Denmark).