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The degree symbol (°, Unicode: U+00B0, HTML: °) is a typographical symbol, or glyph, that is used to represent degrees of arc (see Geographic coordinate system ) or temperature.

Especially in the biological and medical fields, 1°, 2°, and 3° are common abbreviations for primary, secondary, and tertiary. In medical shorthand, the degree symbol is also used to denote hours, for instance q4° or q4° meaning "every four hours."

Due to a similar appearance in some fonts in print and on computer screens, some other characters may be mistakenly substituted for it: the "masculine ordinal indicator" (U+00BA, º ), the "ring above" (U+02DA, ˚ ), "superscript zero" (U+2070, ⁰ ), superscript zero proper ( ⁰ ) or superscript letter "o" ( ^o ), and the "ring operator" (U+2218, ∘ ).

Since at least the age of desktop publishing, personal computers have been able to typographically produce the degree symbol. On Apple Computer's Mac OS, the degree sign can be typed by Option-Shift-8 on most keyboard layouts, including Australian, British, Canadian and U.S. Extended layouts. (Option-K, on the other hand, is "ring above") On Microsoft Windows, the degree sign can be typed by ALT + 0176 on the numeric keypad. On Linux and other Unix-like systems, many keyboard layouts allow typing the degree sign with AltGr+Shift+0.

The degree symbol was originally an ancient symbol representing the Sun.^{[citation needed]}

In the case of degrees of arc, the degree symbol follows the number without intervening space.

In contrast to expressing degrees of arc, in the case of degrees of temperature, several scientific and engineering standards bodies, BIPM and the U.S. Government Printing Office prescribe printing the degree symbol with a space between the degree symbol and the number, as in "10 °C".^[1][2] However, in many professionally typeset works, including scientific works, such as those published by The University of Chicago Press or Oxford University Press, the degree symbol is printed with no spaces between the number, the symbol, and the C or F representing Celsius or Fahrenheit, as in "10°C".^[3] This is also the practice of the University Corporation for Atmospheric Research which operates the National Center for Atmospheric Research.^[4] Still others place the space between the degree sign and the letter (10° C), in a manner probably no longer recommended by any of the major style guides.

Use of the degree symbol to refer to temperatures measured in kelvins (symbol: K) was abolished in 1967 by the 13th General Conference on Weights and Measures (CGPM). Therefore, the freezing point of water, for instance, is today correctly written as simply 273.15 K. The SI fundamental temperature unit is now "kelvin", and no longer "degree Kelvin" (note the lower case).

1. ^ The International System of Units (8th ed.), Bureau International des Poids et Mesures, 2006, <http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf>
2. ^ Style Manual, United States Government Printing Office, 2000, pp. p171, <http://www.gpoaccess.gov/stylemanual/2000/chap10.pdf>
3. ^ Chicago Manual of Style (15th ed.), 2006, <http://www.chicagomanualofstyle.org/home.>
4. ^ UCAR, UCAR Communications Style Guide, <http://www.ucar.edu/communications/styleguide/d.shtml>. Retrieved on 2007-09-01