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Degree symbol | |
| In Unicode | U+00B0 °DEGREE SIGN (°) |
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Thedegree symbol ordegree sign,°, is aglyph orsymbol that is used, among other things, to representdegrees of arc (e.g. ingeographic coordinate systems), hours (in the medical field),degrees of temperature oralcohol proof. The symbol consists of a smallsuperscript circle.
The worddegree is equivalent to Latingradus which, since the medieval period, could refer to any stage in a graded system of ranks or steps. The number of the rank in question was indicated byordinal numbers, inabbreviation with theordinal indicator (a superscript letter⟨o⟩).
Use of "degree" specifically for the degrees of arc, used in conjunction with Arabic numerals, became common in the 16th century, but this was initially without the use of an ordinal marker or degree symbol: instead, various abbreviation ofgradus (e.g., Gra., Gr., gr., G.).[1] The modern notation appears in print in the 1570s, with a borderline example byJacques Pelletier du Mans in 1569, and was popularized by, among others,Tycho Brahe andJohannes Kepler, but didn't become universal.
Similarly, the introduction of thetemperature scales with degrees in the 18th century was at first without such symbols, but with the word "gradus" spelled out. Use of the degree symbol was introduced for temperature in the later 18th century and became widespread in the early 19th century.Antoine Lavoisier in his "Opuscules physiques et chymiques" (1774) used themasculine ordinal indicator with Arabic numerals – for example, when he wrote in the introduction:
The1º. is to be read asprimo meaning "in the first place", followed by2º. (secundo, "in the second place"), etc. In the same work, when Lavoisier gives a temperature, he spells out the word "degree" explicitly.[2]
An early use of the degree symbol for temperature is that byHenry Cavendish in 1776 for degrees of theFahrenheit scale.[3]
The symbol is also declared as a notation for degrees of arc as early as 1831, in an American mathematics textbook for schools.[4]
In the case of degrees ofangulararc, the degree symbol follows the number without any interveningspace, e.g.30°. The addition ofminute and second of arc follows the degree units, with intervening spaces (optionally,non-breaking space) between the sexagesimaldegree subdivisions but no spaces between the numbers and units, for example30° 12′ 5″.
In the case of degrees oftemperature, three scientific and engineering standards bodies (theInternational Bureau of Weights and Measures, theInternational Organization for Standardization and theU.S. Government Printing Office) prescribe printing temperatures with a space between the number and the degree symbol, e.g.10 °C.[5][6] However, in many works with professional typesetting, including scientific works published by theUniversity of Chicago Press orOxford University Press, the degree symbol is printed with no spaces between the number, the symbol, and the Latin letters "C" or "F" representingCelsius orFahrenheit, respectively, e.g.10°C.[7][8] This is also the practice of the University Corporation for Atmospheric Research, which operates the National Center for Atmospheric Research.[9] BothASTM International andNIST, the official US entities related to the standardization of the use of units, require a space between the numerical value and the unit designator,[10] except when the degree symbol alone is used to denote an angular value.
Use of the degree symbol to refer to temperatures measured inkelvins (symbol: K) was abolished in 1967 by the 13th General Conference on Weights and Measures (CGPM). Therefore, the triple point of water, for instance, is written simply as 273.16 K. The name of the SI unit of temperature is now "kelvin", in lower case, and no longer "degrees Kelvin".
Inphotography, the symbol is used to denotelogarithmicfilm speed grades. In this usage, it follows the number without spacing as in21° DIN,5° ASA orISO 100/21°.
The degree symbol is included in Unicode asU+00B0 °DEGREE SIGN (°).
For use withwide character fonts, there are also code points forU+2103 ℃DEGREE CELSIUS andU+2109 ℉DEGREE FAHRENHEIT.
The degree sign was not included in the basic 7-bitASCII set of 1963. In 1987, theISO/IEC 8859 standard introduced it at position 0xB0 (176 decimal) in all variants except Part 5 (Cyrillic), 6 (Arabic), 7 (Greek) and 11 (Thai). In 1991, theUnicode standard incorporated all of the ISO/IEC 8859 part 1 code points and thus included the degree sign at U+00B0.
TheWindows Code Page 1252 was an extension ofISO/IEC 8859-1 (8859 Part 1 or "ISO Latin-1") standard, so it had the degree sign at the same code point, 0xB0. The code point in the older DOSCode Page 437 was 0xF8 (248 decimal); therefore, theAlt code used to enter the symbol directly from the keyboard isAlt+248.
Other characters with similar appearance but different meanings include:
Some computer keyboard layouts, such as theQWERTY layout as used in Italy, theQWERTZ layout as used in Germany, Austria and Switzerland, and theAZERTY layout as used in France and Belgium, have the degree symbol available directly on a key. But the common keyboard layouts in English-speaking countries do not include the degree sign, which then has to be input some other way. The method of inputting depends on theoperating system andkeyboard mapping being used.
Degrees are marked at the top of the figure with asmall °, minutes with′, seconds with ″ and so on.(It is possibly used in earlier editions but these are not available online.)