Unicode subscripts and superscripts

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

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

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The intended use[2] when these characters were added to Unicode was to produce true superscripts and subscripts so that chemical and algebraic formulas could be written without markup. Thus "H₂O" (using a subscript 2 character) is supposed to be identical to "H2O" (with subscript markup).

In reality, many fonts that include these characters ignore the Unicode definition, and instead design the digits for mathematical numerator and denominator glyphs,[3][4] which are aligned with the cap line and the baseline, respectively. When used with the solidus, these glyphs are a common substitute for diagonal fractions, such as ³/₄ for the ¾ glyph. This change was made because using markup does not give a good graphic approximation of fractions (compare markup 3/4 with super/sub-script ³/₄). The change also makes the superscript letters useful for ordinal indicators, more closely matching the ª and º characters. However, it makes them incorrect for normal superscript and subscript, and so chemical and algebraic formulas are better rendered by using markup.

Unicode intended that diagonal fractions be rendered by a different mechanism: the fraction slash U+2044 is visually similar to the solidus, but when used with the ordinary digits (not the superscripts and subscripts), it instructs the layout system that a fraction such as ¾ is to be rendered using automatic glyph substitution.[5][a] User-end support was quite poor for a number of years, but fonts, browsers,[b] word processors,[c] desktop publishing software[d] and others increasingly support the intended Unicode behavior.

A selection of supporting fonts is displayed in the table below. (These will not display properly if you do not have the fonts installed, or if your browser does not support this behavior.)

Comparison of encodings of simple fractions, superscripts and subscripts
Font
U+00BD VULGAR
FRACTION ONE HALF
U+0031 DIGIT ONE
U+2044 FRACTION SLASH
U+0032 DIGIT TWO
U+00B9 SUPERSCRIPT ONE
U+2044 FRACTION SLASH
U+2082 SUBSCRIPT TWO
Browser default font ½ 1⁄2 ¹⁄₂
Andika ½ 1⁄2 ¹⁄₂
Arno Pro ½ 1⁄2 ¹⁄₂
URW Bookman ½ 1⁄2 ¹⁄₂
Brill ½ 1⁄2 ¹⁄₂
Brioso Pro ½ 1⁄2 ¹⁄₂
Calibri ½ 1⁄2 ¹⁄₂
Candara ½ 1⁄2 ¹⁄₂
Carlito ½ 1⁄2 ¹⁄₂
Cantarell ½ 1⁄2 ¹⁄₂
FiraGO ½ 1⁄2 ¹⁄₂
EB Garamond ½ 1⁄2 ¹⁄₂
Gentium Book ½ 1⁄2 ¹⁄₂
URW Gothic ½ 1⁄2 ¹⁄₂
Lato ½ 1⁄2 ¹⁄₂
Linux Libertine ½ 1⁄2 ¹⁄₂
Nimbus Roman ½ 1⁄2 ¹⁄₂
Nimbus Sans ½ 1⁄2 ¹⁄₂
Noto Sans ½ 1⁄2 ¹⁄₂
Noto Serif ½ 1⁄2 ¹⁄₂
Open Sans ½ 1⁄2 ¹⁄₂
Yrsa ½ 1⁄2 ¹⁄₂

Superscripts and subscripts block

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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 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 xₔ xₕ xₖ xₗ xₘ xₙ xₚ xₛ xₜ
HTML formatting using <sup> and <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 xə 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

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Unicode version 16.0 also includes subscript and superscript characters that are intended for semantic usage, in the following blocks:[1][6]

Superscript
  • The Latin-1 Supplement block contains the feminine and masculine ordinal indicators ª and º.
  • The Latin Extended-C block contains one superscript, ⱽ.
  • The Latin Extended-D block contains six superscripts: ꝰ ꟲ ꟳ ꟴ ꟸ ꟹ.
  • The Latin Extended-E block contains five superscripts: ꭜ ꭝ ꭞ ꭟ ꭩ.
  • The Latin Extended-F block is entirely superscript IPA letters: 𐞁 𐞂 𐞃 𐞄 𐞅 𐞇 𐞈 𐞉 𐞊 𐞋 𐞌 𐞍 𐞎 𐞏 𐞐 𐞑 𐞒 𐞓 𐞔 𐞕 𐞖 𐞗 𐞘 𐞙 𐞚 𐞛 𐞜 𐞝 𐞞 𐞟 𐞠 𐞡 𐞢 𐞣 𐞤 𐞥 𐞦 𐞧 𐞨 𐞩 𐞪 𐞫 𐞬 𐞭 𐞮 𐞯 𐞰 𐞲 𐞳 𐞴 𐞵 𐞶 𐞷 𐞸 𐞹 𐞺.
  • The Spacing Modifier Letters block has superscripted letters and symbols used for phonetic transcription: ʰ ʱ ʲ ʳ ʴ ʵ ʶ ʷ ʸ ˀ ˁ ˠ ˡ ˢ ˣ ˤ.
  • The Phonetic Extensions block has several superscripted letters and symbols: Latin/IPA ᴬ ᴭ ᴮ ᴯ ᴰ ᴱ ᴲ ᴳ ᴴ ᴵ ᴶ ᴷ ᴸ ᴹ ᴺ ᴻ ᴼ ᴽ ᴾ ᴿ ᵀ ᵁ ᵂ ᵃ ᵄ ᵅ ᵆ ᵇ ᵈ ᵉ ᵊ ᵋ ᵌ ᵍ ᵏ ᵐ ᵑ ᵒ ᵓ ᵖ ᵗ ᵘ ᵚ ᵛ, Greek ᵝ ᵞ ᵟ ᵠ ᵡ, Cyrillic ᵸ, other ᵎ ᵔ ᵕ ᵙ ᵜ. These are intended to indicate secondary articulation.
  • The Phonetic Extensions Supplement block has several more: Latin/IPA ᶛ ᶜ ᶝ ᶞ ᶟ ᶠ ᶡ ᶢ ᶣ ᶤ ᶥ ᶦ ᶧ ᶨ ᶩ ᶪ ᶫ ᶬ ᶭ ᶮ ᶯ ᶰ ᶱ ᶲ ᶳ ᶴ ᶵ ᶶ ᶷ ᶸ ᶹ ᶺ ᶻ ᶼ ᶽ ᶾ, Greek ᶿ.
  • The Cyrillic Extended-B block contains two Cyrillic superscripts: ꚜ ꚝ.
  • The Cyrillic Extended-D block contains many Cyrillic superscripts: 𞀰 𞀱 𞀲 𞀳 𞀷 𞀵 𞀶 𞀷 𞀸 𞀹 𞀺 𞀻 𞀼 𞀽 𞀾 𞀿 𞁀 𞁁 𞁂 𞁃 𞁄 𞁅 𞁆 𞁇 𞁈 𞁉 𞁊 𞁋 𞁌 𞁍 𞁎 𞁏 𞁐 𞁫 𞁬 𞁭.
  • The Georgian block contains one superscripted Mkhedruli letter: ჼ.
  • The Kanbun block has superscripted annotation characters used in Japanese copies of Classical Chinese texts: ㆒ ㆓ ㆔ ㆕ ㆖ ㆗ ㆘ ㆙ ㆚ ㆛ ㆜ ㆝ ㆞ ㆟.
  • The Tifinagh block has one superscript letter : ⵯ.
  • The Unified Canadian Aboriginal Syllabics and its Extended blocks contain several mostly consonant-only letters to indicate syllable coda called Finals, along with some characters that indicate syllable medial known as Medials: Main block ᐜ ᐝ ᐞ ᐟ ᐠ ᐡ ᐢ ᐣ ᐤ ᐥ ᐦ ᐧ ᐨ ᐩ ᐪ ᑉ ᑊ ᑋ ᒃ ᒄ ᒡ ᒢ ᒻ ᒼ ᒽ ᒾ ᓐ ᓑ ᓒ ᓪ ᓫ ᔅ ᔆ ᔇ ᔈ ᔉ ᔊ ᔋ ᔥ ᔾ ᔿ ᕀ ᕁ ᕐ ᕑ ᕝ ᕪ ᕻ ᕯ ᕽ ᖅ ᖕ ᖖ ᖟ ᖦ ᖮ ᗮ ᘁ ᙆ ᙇ ᙚ ᙾ ᙿ; Extended block: ᣔ ᣕ ᣖ ᣗ ᣘ ᣙ ᣚ ᣛ ᣜ ᣝ ᣞ ᣟ ᣳ ᣴ ᣵ.
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 uͤ. They are shown here over the dotted circle placeholder ◌: ◌ͣ ◌ͤ ◌ͥ ◌ͦ ◌ͧ ◌ͨ ◌ͩ ◌ͪ ◌ͫ ◌ͬ ◌ͭ ◌ͮ ◌ͯ.
  • The Combining Diacritical Marks Extended block contains three combining insular letters for the Middle English Ormulum, ◌ᫌ ◌ᫍ ◌ᫎ.[7]
  • 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: ◌᷒ ◌ᷓ ◌ᷔ ◌ᷕ ◌ᷖ ◌ᷗ ◌ᷘ ◌ᷙ ◌ᷚ ◌ᷛ ◌ᷜ ◌ᷝ ◌ᷞ ◌ᷟ ◌ᷠ ◌ᷡ ◌ᷢ ◌ᷣ ◌ᷤ ◌ᷥ ◌ᷦ ◌ᷧ ◌ᷨ ◌ᷪ ◌ᷫ ◌ᷬ ◌ᷭ ◌ᷮ ◌ᷯ ◌ᷰ ◌ᷱ ◌ᷲ ◌ᷳ ◌ᷴ, Greek ◌ᷩ.
  • 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 (ст): ◌ⷠ ◌ⷡ ◌ⷢ ◌ⷣ ◌ⷤ ◌ⷥ ◌ⷦ ◌ⷧ ◌ⷨ ◌ⷩ ◌ⷪ ◌ⷫ ◌ⷬ ◌ⷭ ◌ⷮ ◌ⷯ ◌ⷰ ◌ⷱ ◌ⷲ ◌ⷳ ◌ⷴ ◌ⷵ ◌ⷶ ◌ⷷ ◌ⷸ ◌ⷹ ◌ⷺ ◌ⷻ ◌ⷼ ◌ⷽ ◌ⷾ ◌ⷿ ◌ꙴ ◌ꙵ ◌ꙶ ◌ꙷ ◌ꙸ ◌ꙹ ◌ꙺ ◌ꙻ ◌ꚞ ◌ꚟ.
  • The Cyrillic Extended-D block has one additional combining character, that being і: ◌𞂏.
Subscript
  • The Latin Extended-C block contains one subscript, ⱼ.
  • The Phonetic Extensions block has several subscripted letters and symbols: Latin/IPA ᵢ ᵣ ᵤ ᵥ and Greek ᵦ ᵧ ᵨ ᵩ ᵪ.
  • The Cyrillic Extended-D block also contains many Cyrillic subscripts: 𞁑 𞁒 𞁓 𞁔 𞁕 𞁖 𞁗 𞁘 𞁙 𞁚 𞁛 𞁜 𞁝 𞁞 𞁟 𞁠 𞁡 𞁢 𞁣 𞁤 𞁥 𞁦 𞁧 𞁨 𞁩 𞁪.
Combining subscript

Latin, Greek, Cyrillic, and IPA tables

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Consolidated, the Unicode standard contains superscript and subscript versions of a subset of Latin, Greek and Cyrillic 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 or 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.

Little punctuation is encoded. Parentheses are shown above in the basic block above, and the exclamation mark ⟨⟩ is shown in the IPA table below. A question mark may be created with a superscript gelded question mark and a combining dot: ⟨ˀ̣⟩, although some fonts do not render it properly.

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 ᴿ
Superscript small cap 𐞄 𐞒 𐞖 𐞪 𐞲
Superscript minuscule ʰ ʲ ˡ 𐞥 ʳ ˢ ʷ ˣ ʸ
Overscript small cap ◌ᷛ ◌ᷞ ◌ᷟ ◌ᷡ ◌ᷢ
Overscript minuscule ◌ͣ ◌ᷨ ◌ͨ ◌ͩ ◌ͤ ◌ᷫ ◌ᷚ ◌ͪ ◌ͥ ◌ᷜ ◌ᷝ ◌ͫ ◌ᷠ ◌ͦ ◌ᷮ ◌ͬ ◌ᷤ ◌ͭ ◌ͧ ◌ͮ ◌ᷱ ◌ͯ ◌ᷦ
Subscript minuscule
Underscript minuscule ◌᷊ ◌ᪿ

Additional superscript capitals are ᴭ ᴯ ᴲ ᴻ. Some of these are small caps in the source documents in the Unicode proposals.
Superscript capital s has been proposed for a future version of the Unicode Standard.[8][9]
Superscript versons of small capital A and E have been proposed for a future version of the Unicode Standard.[10][11][9]

Greek superscript and subscript letters
Α Β Γ Δ Ε Ζ Η Θ Ι Κ Λ Μ Ν Ξ Ο Π Ρ Σ Τ Υ Φ Χ Ψ Ω
Superscript minuscule [A] ᶿ [A]
Overscript minuscule ◌ᷧ ◌ᷩ
Subscript minuscule ͺ[12]
Underscript minuscule ◌ͅ ◌̫[13]
  1. ^ a b In some fonts, Latin alpha ᵅ and upsilon ᶹ can be used as superscript Greek alpha and upsilon. ᵋ and ᶥ are also officially Latin letters, but display the same as Greek.

Superscript versons of Greek psi and omega have been proposed for a future version of the Unicode Standard.[10][9]

Cyrillic superscript and subscript letters
А Ә Б В Г Ґ Д Е Є Ж З Ѕ И І Ї Ј К Л М Н О Ө П Р С Ҫ
Superscript 𞀰 𞁋 𞀱 𞀲 𞀳 𞀴 𞀵 𞀶 𞀷 𞁊 𞀸 𞁌 𞁍 𞀹 𞀺 𞀻 𞀼 𞁎 𞀽 𞀾 𞀿 𞁫
Overscript ◌ⷶ ◌ⷠ ◌ⷡ ◌ⷢ ◌ⷣ ◌ⷷ ◌ꙴ ◌ⷤ ◌ⷥ ◌ꙵ ◌𞂏 ◌ꙶ ◌ⷦ ◌ⷧ ◌ⷨ ◌ⷩ ◌ⷪ ◌ⷫ ◌ⷬ ◌ⷭ
Subscript 𞁑 𞁒 𞁓 𞁔 𞁧 𞁕 𞁖 𞁗 𞁘 𞁩 𞁙 𞁨 𞁚 𞁛 𞁜 𞁝 𞁞
Т У Ү Ұ Ф Х Ѡ Ц Ч Џ Ш Щ Ъ Ы Ь Ѣ Э Ю Ѥ Ѧ Ѫ Ѭ Ѳ Ӏ
Superscript 𞁀 𞁁 𞁏 𞁭 𞁂 𞁃 𞁄 𞁅 𞁆 𞁬 𞁇 𞁈 𞁉 𞁐
Overscript ◌ⷮ ◌ꙷ ◌ⷹ ◌ꚞ ◌ⷯ ◌ꙻ ◌ⷰ ◌ⷱ ◌ⷲ ◌ⷳ ◌ꙸ ◌ꙹ ◌ꙺ ◌ⷺ ◌ⷻ ◌ⷼ ◌ꚟ ◌ⷽ ◌ⷾ ◌ⷿ ◌ⷴ
Subscript 𞁟 𞁠 𞁡 𞁢 𞁣 𞁪 𞁤 𞁥 𞁦

Many of the Cyrillic characters were added to the Cyrillic Extended-D block, which was added to the free Gentium Plus and Andika fonts with version 6.2 in February 2023.

See also small caps in Unicode.

Superscript IPA

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The Latin Extended-F block was created for the remaining superscript IPA letters. They are supported by the free Gentium Plus and Andika fonts. Additional superscript characters for historical and para-IPA letters have been proposed for future versions of the Unicode Standard.[11][9]

Length marks
Long Half-long
ː 𐞁
10781
ˑ 𐞂
10782

These are used to add length to another superscript, such as long aspiration.

Wildcards

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Superscript wildcards (full caps) are largely supported: e.g. ᴺC (prenasalized consonant), ꟲN (prestopped nasal), Pꟳ (fricative release), NᴾF (epenthetic plosive), CVNᵀ (tone-bearing syllable), Cᴸ (liquid or lateral release), Cᴿ (rhotic or resonant release), Vᴳ (off-glide/diphthong), Cⱽ (fleeting vowel). Superscript S for sibilant release has been proposed for a future version of the Unicode Standard;[8][9] superscript for fleeting/epenthetic click has not. Other basic Latin superscript wildcards for tone and weak indeterminate sounds, as described in the article on the International Phonetic Alphabet, are mostly supported. (See table in previous section.)

Combining marks and subscripts

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In addition, a very few IPA letters beyond the basic Latin alphabet have combining forms or are supported as subscripts:

Additional IPA characters
ä ɑ æ ç ð ə ʃ ʍ ʔ ʼ
Overscript ◌ᷲ ◌ᷧ ◌ᷔ ◌ᷗ ◌ᷙ ◌ᷪ ◌ᷯ ◌̉[e] ◌̓
Subscript
Underscript ◌ᫀ ◌̦

Composite characters

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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.

Notes

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  1. ^ For a general overview and technical information on glyph substitution (though not specifically for fractions), see GSUB — Glyph Substitution Table in the OpenType specification on the Microsoft Typography site.
  2. ^ Such as Chrome, Firefox and Falkon
  3. ^ Such as LibreOffice Writer
  4. ^ Such as Adobe InDesign and Scribus
  5. ^ This is actually the Vietnamese diacritic dấu hỏi, not specifically IPA, but graphically both are gelded question marks.

References

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  1. ^ a b c "UCD: UnicodeData.txt". The Unicode Standard. Retrieved 2016-05-14.
  2. ^ a b Martin Dürst, Asmus Freytag (16 May 2007). "Unicode in XML and other Markup Languages". W3C. Retrieved 13 September 2010.
  3. ^ "fraction | Dart Package". Dart packages. 27 December 2021. Retrieved 21 September 2022.
  4. ^ "MathML | General layout elements | Fractions". data2type GmbH (in German). 30 March 2021. Retrieved 13 January 2022.[dead link]
  5. ^ Martin Dürst, Asmus Freytag (16 May 2007). "Fraction Slash". W3C. Retrieved 13 September 2010.
  6. ^ "UCD: Scripts.txt". The Unicode Standard. Retrieved 2022-09-21.
  7. ^ Everson, Michael; West, Andrew (2020-10-05). "L2/20-268: Revised proposal to add ten characters for Middle English to the UCS" (PDF).
  8. ^ a b Kirk Miller (2024-01-30). "L2/24-081: Unicode request for modifier capital S" (PDF).
  9. ^ a b c d e "Proposed New Characters: Pipeline Table". Unicode Consortium. 2024-09-10. Retrieved 2024-09-21.
  10. ^ a b Kirk Miller (2024-06-14). "L2/24-147: Modifier Sinological extensions to the IPA" (PDF).
  11. ^ a b Kirk Miller (2024-06-06). "L2/24-171: Miscellaneous historical and para-IPA modifier letters" (PDF).
  12. ^ ͺ⟩ is set lower than a normal subscript. It is equivalent to underscript ⟨◌ͅ⟩ on a space.
  13. ^ ◌̫⟩ is traditionally typeset as an omega.
  14. ^ Silva, Eduardo Marín (2017-03-01). "L2/17-066R: Proposal to encode the Marca Registrada sign" (PDF).