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The difference between superscript/subscript and numerator/denominator glyphs. In many popular fonts the Unicode "superscript" and "subscript" characters are actually numerator and denominator glyphs.

Unicode has subscripted and superscripted versions of a number of characters including a full set of Arabic numerals.[1] These characters allow any polynomial, chemical and certain other equations to be represented in plain text without using any form of markup like HTML or TeX.

The World Wide Web Consortium and the Unicode Consortium have made recommendations on the choice between using markup and using superscript and subscript characters:

When used in mathematical context (MathML) it is recommended to consistently use style markup for superscripts and subscripts.... However, when super and sub-scripts are to reflect semantic distinctions, it is easier to work with these meanings encoded in text rather than markup, for example, in phonetic or phonemic transcription.[2]

Uses

The intended use[2] when these characters were added to Unicode was to allow chemical and algebra formulas and phonetics to be written without markup, but produce true superscripts and subscripts. Thus "H?O" (using a subscript character) is supposed to be identical to "H2O" (with subscript markup).

In reality most fonts that include these characters ignore the Unicode definition, and design the digits for mathematical numerator and denominator glyphs,[] which are smaller than normal characters but are aligned with the cap line and the baseline, respectively. When used with the solidus, these glyphs are useful for making arbitrary diagonal fractions (similar to the ½ glyph). Making fractions using existing software super/subscripts requires many characters and does not look like the rendered fraction (example: 1/2), so font designers provided this alternative. This also makes the superscript letters useful for ordinal indicators, more closely matching the ª and º characters. However it makes them incorrect for normal super and subscripts, and formulas are rendered correctly by using markup rather than these characters.

Unicode intended to produce diagonal fractions through a different mechanism but it is very poorly supported. The fraction slash U+2044 is visually similar to the solidus, but when used with the ordinary digits (not the superscripts and subscripts) is intended to tell a layout system that a fraction such as ¾ should be rendered[3] using automatic glyph substitution[a] for the digits. Some browsers support this[b] but not in all fonts. A selection of fonts is shown in the below table.

Characters Font Result
½ VULGAR FRACTION ONE HALF Default ½
¹ SUPERSCRIPT ONE, / SOLIDUS, SUBSCRIPT TWO ¹/?
¹ SUPERSCRIPT ONE, FRACTION SLASH, SUBSCRIPT TWO ¹/?
1 DIGIT ONE,
FRACTION SLASH,
2 DIGIT TWO
1/2
Arial 1/2
Cambria 1/2
Consolas 1/2
Times New Roman 1/2
FiraGO 1/2
EB Garamond 1/2
Cantarell 1/2
Lato 1/2
Linux Libertine O 1/2
Nimbus Roman 1/2
Ubuntu 1/2
Yrsa 1/2

Superscripts and subscripts block

The most common superscript digits (1, 2, and 3) were in ISO-8859-1 and were therefore carried over into those positions in the Latin-1 range of Unicode. The rest were placed in a dedicated section of Unicode at U+2070 to U+209F. The two tables below show these characters. Each superscript or subscript character is preceded by a normal x to show the subscripting/superscripting. The table on the left contains the actual Unicode characters; the one on the right contains the equivalents using HTML markup for the subscript or superscript.

Unicode characters
0 1 2 3 4 5 6 7 8 9 A B C D E F
U+00Bx
U+207x x? x? x? x? x? x? x? x? x? x? x? x? x? x?
U+208x x? x? x? x? x? x? x? x? x? x? x? x? x? x? x?
U+209x x? x? x? x? x? x? x? x? x? x? x? x? x?
Simulated using `<sup>` or `<sub>` tags
0 1 2 3 4 5 6 7 8 9 A B C D E F
U+00Bx x2 x3 x1
U+207x x0 xi x4 x5 x6 x7 x8 x9 x+ x x= x( x) xn
U+208x x0 x1 x2 x3 x4 x5 x6 x7 x8 x9 x+ x x= x( x)
U+209x xa xe xo xx x? xh xk xl xm xn xp xs xt
Reserved for future use.
Other characters from Latin-1 not related to super- or sub-scripts.

Other superscript and subscript characters

Unicode version 13.0 also includes subscript and superscript characters that are intended for semantic usage, in the following blocks:[1][4]

Superscript
Combining superscript
• The Combining Diacritical Marks block contains medieval superscript letter diacritics. These letters are written directly above other letters appearing in medieval Germanic manuscripts, and so these glyphs do not include spacing, for example u?. They are shown here over the dotted circle placeholder .
• The Combining Diacritical Marks Extended block contains two combining letters for linguistic transcriptions of Scots? .
• The Combining Diacritical Marks Supplement block contains additional medieval superscript letter diacritics, enough to complete the basic lowercase Latin alphabet except for j, q and y, a few small capitals and ligatures (ae, ao, av), and additional letters? .
• The Cyrillic Extended-A and -B blocks contains multiple medieval superscript letter diacritics, enough to complete the basic lowercase Cyrillic alphabet used in Church Slavonic texts, also includes an additional ligature (): .
Subscript
• The Latin Extended-C block contains one additional subscript, ?.
• The Spacing Modifier Letters block has superscripted letters and symbols used for phonetic transcription ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?.
• The Phonetic Extensions block has several subscripted letters and symbols: Latin/IPA ? ? ? ? and Greek ? ? ? ? ?.
Combining subscript

Latin and Greek tables

Consolidated, the Unicode standard contains superscript and subscript versions of a subset of Latin and Greek letters. Here they are arranged in alphabetical order for comparison (or for copy and paste convenience). Since these characters appear in different Unicode ranges, they may not appear to be the same size and position due to font substitution in the browser. Shaded cells mark small capitals that are not very distinct from minuscules, and Greek letters that are indistinguishable from Latin, and so would not be expected to be supported by Unicode. Asterisks are placeholders for characters provisionally accepted for Unicode 14, to be published in 2021.[5]

Latin superscript and subscript letters
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Superscript capital ? ? * ? ? * ? ? ? ? ? ? ? ? ? ? * ? ? ? ? ?
Superscript small cap * * * ? ? ? * ? *
Superscript minuscule ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? * ? ? ? ? ? ? ? ? ?
Overscript small cap
Overscript minuscule
Subscript minuscule ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Underscript minuscule
Greek superscript and subscript letters
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Superscript minuscule ? ? ? ? ? ?
Overscript minuscule
Subscript minuscule ? ? ? ? ?

For basic IPA, see superscript IPA letters. Other phonetic symbols are,

other IPA superscript and subscript letters
? æ ç ð ? ? ? ? ? ? ?
Superscript ? [c] ? ? ? ? ? ? ? ?
Overscript
Subscript ?
Underscript

Composite characters

Primarily for compatibility with earlier character sets, Unicode contains a number of characters that compose super- and subscripts with other symbols.[1] In most fonts these render much better than attempts to construct these symbols from the above characters or by using markup.

• The Unified Canadian Aboriginal Syllabics and its Extended blocks contain several letters composed with superscripted letters to indicate extended sound values: Main block ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?, Extended block ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?.

Notes

1. ^ For a general overview and technical information on glyph substitution (though not specifically for fractions): GSUB -- Glyph Substitution Table in the OpenType specification on the Microsoft Typography site.
2. ^ Such as Chrome on Windows, Firefox[failed verification]
3. ^ Superscript ⟨ç⟩ is composed of superscript ⟨c⟩ and a combining cedilla, which should display properly in a good font. Superscript ⟨c⟩ was specifically requested for this purpose in Unicode proposal L2/03-180.

References

1. ^ a b c "UCD: UnicodeData.txt". The Unicode Standard. Retrieved .
2. ^ a b Martin Dürst, Asmus Freytag (16 May 2007). "Unicode in XML and other Markup Languages". W3C. Retrieved 2010.
3. ^ Martin Dürst, Asmus Freytag (16 May 2007). "Fraction Slash". W3C. Retrieved 2010.
4. ^ "UCD: Scripts.txt". The Unicode Standard. Retrieved .
5. ^ [1]
6. ^ Silva, Eduardo Marín (2017-03-01). "L2/17-066R: Proposal to encode the Marca Registrada sign" (PDF).