Wikipedia:Manual of Style/Superscripts and subscripts

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A Superscript or a Subscript is text that is positioned slightly above or below the normal line of type and is sometimes rendered in a smaller font. This part of the Manual of Style aims to achieve consistency in the use and formatting of superscripts and subscripts in Wikipedia articles.

Do not use the  and  HTML tags, respectively, with no other formatting info. The {{sup}} and {{sub}} templates are useful shortcuts to the HTML markup. Use the Unicode subscripts and superscripts ² and ³, or XML/HTML character entity references (² etc). Do not write 2 and 3 to produce the superscripts ² and ³, because they are not customizable by the font designer. The superscripted 2 and 3 are easier to read, especially on small displays, and ensure that exponents are properly aligned. Compare:

wⁱx²z⁽ⁿ⁺⁶⁾ (Unicode superscripts) to

wⁱx²z^{(n + 6)} (wix2z(n + 6)) or

wⁱx²z^{(n + 6)} (w{{sup|i}}x{{sup|2}}z{{sup|(n + 6)}})

1 + x² + y³ (²) to

1 + x² + y³ (2) or

1 + x² + y³ ({{sup|2}})

Except under extraordinary circumstances, font sizes, color, etc. should be controlled with Wikipedia's stylesheets.

Dates and numbers

The ordinal suffix (e.g., th) is not superscripted (23rd and 496th, not 23ʳᵈ and 496ᵗʰ).
Centuries and millennia are written using ordinal numbers, without superscripts and without Roman numerals: the second millennium, the 19th century, a 19th-century book (see also Wikipedia:Manual of Style#Numbers as figures or words).
Non-base-10 notations in non-computer-related articles use subscript notation. For example: 137₉, 241₅, 2A9₁₂, A87D₁₆ (use ₀, ₁, ₂, ₃, ₄, ₅, ₆, ₇, ₈, ₉).

Music

In figured bass, superscript and subscript may be combid by using math markup or by using the {{su}} template: <math>C_6^4</math> = $C_{6}^{4}$ , ''C''{{su|b=6|p=4}} = C⁴
₆; (see also Wikipedia:TeX markup or m:Help:Formula).
A superscript circle, or degree sign, which indicates a diminished chord, that may not display correctly for everyone, "°", can be produced by typing °, &#176, or by keying Alt+0176 (Windows PCs). A superscript lower case "^o" ({{sup|o}}) may not be used instead. The slashed o, "^ø", which may not display correctly for all readers, is produced by superscripting the character produced by typing ø, or ø, or by keying Alt+0248 (Windows PCs).
For inversions and the degree sign superscript and subscript may be done thus: vii{{sup|o}}, I{{sub|6}}. This looks like: vii^o, I₆.

Unit symbols and abbreviations

Squared and cubic metric-symbols are always expressed with a superscript exponent (5 km², 2 cm³); squared imperial and US unit abbreviations may be rendered with sq, and cubic with cu (15 sq mi, 3 cu ft).

Science

Chemistry

Descriptions of:

Chemical compounds

C₂H₅OH using C₂H₅OH

Isotopes

³
₂He using {{Nuclide2|He|3}}

Mathematics

Exponentiation is indicated using a superscript:

2² = 4 using 2² = 4

Special care is needed with subscripted labels to distinguish the purpose of the subscript (as this is a common error): variables and constants in subscripts should be italic, while textual labels should be in normal text font (Roman, upright). For example:

x_{\text{this one}}=y_{\text{that one}}\,\!

(correct—typeset from <math> x_\text{this one} = y_\text{that one} \,\!</math>),

and

\sum _{i=1}^{n}{y_{i}^{2}}\!

(correct—typeset from <math>\sum_{i=1}^n { y_i^2 }\!</math>),

but not

r=x_{predicted}-x_{observed}

(incorrect—typeset from r = x_{predicted} - x_{observed}).

Moreover, the TeX engine used on Wikipedia may format simple superscripts using ... depending on user preferences. Thus, instead of the image $x^{2}\,$ , many users see x². Formulae formatted without using TeX should use the same syntax to maintain the same appearance.