Degree symbol

The degree symbol or degree sign, °, is a typographical symbol that is used, among other things, to represent degrees of arc (e.g. in geographic coordinate systems), hours (in the medical field), degrees of temperature or alcohol proof. The symbol consists of a small raised circle, historically a zero glyph.

History[]

The first known recorded modern use of the degree symbol in mathematics is from 1657,^{[1][failed verification]} where the usage seems to show that the symbol is a small raised zero, to match the prime symbol notation of sexagesimal subdivisions of degree such as minute ′, second ″, and third ‴, which originated as small raised Roman numerals.^{[citation needed]}

Typography[]

In the case of degrees of angular arc, the degree symbol follows the number without any intervening space, e.g. 30°. The addition of minute and second of arc follows the degree units, with intervening spaces (optionally, non-breaking space) between the sexagesimal degree subdivisions but no spaces between the numbers and units, for example 30° 12′ 5″.

In the case of degrees of temperature, three scientific and engineering standards bodies (the International Bureau of Weights and Measures, the International Organization for Standardization and the U.S. Government Printing Office) prescribe printing temperatures with a space between the number and the degree symbol, e.g. 10 °C.^[2][3] However, in many works with professional typesetting, including scientific works 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 Latin letters "C" or "F" representing Celsius or Fahrenheit, respectively, e.g. 10°C.^[4][5] This is also the practice of the University Corporation for Atmospheric Research, which operates the National Center for Atmospheric Research.^[6]

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 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".

In photography, the symbol is used to denote logarithmic film speed grades. In this usage, it follows the number without spacing as in 21° DIN, 5° ASA or ISO 100/21°.

Encoding[]

The degree symbol is included in Unicode as U+00B0 ° DEGREE SIGN (HTML ° · °).

For use with Chinese characters there are also code points for U+2103 ℃ DEGREE CELSIUS (HTML ℃) and U+2109 ℉ DEGREE FAHRENHEIT (HTML ℉).

The degree sign was missing from the basic 7-bit ASCII set of 1963, but in 1987 the ISO/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 the Unicode standard incorporated all of the ISO/IEC 8859 code points, including the degree sign (at U+00B0)..

The Windows Code Page 1252 was also an extension of ISO/IEC 8859-1 (Part 1 or Latin-1) standard, so it had the degree sign at the same code point, 0xB0. The code point in the older DOS Code Page 437 was 0xF8 (248 decimal); therefore, the Alt code used to enter the symbol directly from the keyboard is Alt+248.

Lookalikes[]

Other characters with similar appearance but different meanings include:

• U+00BA º MASCULINE ORDINAL INDICATOR (HTML º · º) (indicator used in Italian, Spanish and Portuguese that follows a numeral denoting that it is an ordinal number, rather than a cardinal number; varies with the font and sometimes underlined)
• U+1D52 ᵒ MODIFIER LETTER SMALL O (HTML ᵒ) (superscript letter o)
• U+02DA ˚ RING ABOVE (HTML ˚ · ˚) (standalone)
  • U+030A ◌̊ COMBINING RING ABOVE (HTML ̊) (applied to a letter)
  • U+0325 ◌̥ COMBINING RING BELOW (HTML ̥) (applied to a letter)
  • U+0366 ◌ͦ COMBINING LATIN SMALL LETTER O (HTML ͦ) (applied to a letter)
• U+309C ゜ KATAKANA-HIRAGANA SEMI-VOICED SOUND MARK (HTML ゜) (standalone)
  • U+309A ◌゚ COMBINING KATAKANA-HIRAGANA SEMI-VOICED SOUND MARK (HTML ゚) (applied to a letter)
  • (precomposed characters containing this mark also exists)
• U+18DE ᣞ CANADIAN SYLLABICS FINAL SMALL RING (HTML ᣞ) (stand alone, typically representing either ⟨w⟩ or ⟨y⟩)
  • (precomposed characters containing this mark also exists)
• U+2070 ⁰ SUPERSCRIPT ZERO (HTML ⁰)
  • U+2080 ₀ SUBSCRIPT ZERO (HTML ₀)
• U+2218 ∘ RING OPERATOR (HTML ∘ · ∘, ∘)
• U+29B5 ⦵ CIRCLE WITH HORIZONTAL BAR (HTML ⦵ · ⦵) (used in superscripted form, ^⦵, to mean standard state (chemistry))
• U+1BC85