Asubscript orsuperscript is a character (such as a number or letter) that is set slightly below or above the normal line of type, respectively. It is usually smaller than the rest of the text. Subscripts appear at or below thebaseline, while superscripts are above. Subscripts and superscripts are perhaps most often used informulas, mathematicalexpressions, and specifications ofchemical compounds andisotopes, but have many other uses as well.

In professionaltypography, subscript and superscript characters are not simply ordinary characters reduced in size; to keep them visually consistent with the rest of the font, typeface designers make them slightly heavier (i.e. medium or bold typography) than a reduced-size character would be. The vertical distance that sub- or superscripted text is moved from the original baseline varies by typeface and by use.

In typesetting, such types are traditionally called "superior" and "inferior" letters, figures, etc., or just "superiors" and "inferiors". In English, most nontechnical use of superiors is archaic.^[1] Superior and inferior figures on the baseline are used forfractions and most other purposes, while lowered inferior figures are needed for chemical and mathematical subscripts.^[2]

A single typeface may contain sub- and superscript glyphs at different positions for different uses. The four most common positions are listed here. Because each position is used in different contexts, not all alphanumerics may be available in all positions. For example, subscript letters on the baseline are quite rare, and many typefaces provide only a limited number of superscripted letters. Despite these differences, all reduced-size glyphs go by the same generic termssubscript andsuperscript, which are synonymous with the termsinferior letter (ornumber) andsuperior letter (ornumber), respectively. Most fonts that contain superscript/subscript will have predetermined size and orientation that is dependent on the design of the font.

Subscripts are used inchemical formulas. For example, the chemical formula forglucose isC₆H₁₂O₆ (meaning that it is a molecule with 6carbon atoms, 12hydrogen atoms and 6oxygen atoms). The chemical formula of thewater molecule, H₂O, indicates that it contains two hydrogen atoms and one oxygen atom.

A subscript is also used to distinguish between different versions of asubatomic particle. Thus electron, muon, and tauneutrinos are denoted
ν
_e
ν
_μ and
ν
_τ. A particle may be distinguished by multiple subscripts, such as
Ω⁻
_bbb for thetriple bottom omega particle.

Similarly, subscripts are also used frequently in mathematics to define different versions of the samevariable: for example, in an equationx₀ andx_f might indicate the initial and final value ofx, whilev_rocket andv_observer would stand for the velocities of a rocket and an observer. Commonly, variables with a zero in the subscript are referred to as the variable name followed by "nought" (e.g. v₀ would be read, "v-nought").^[3]

Subscripts are often used to refer to members of a mathematicalsequence orset or elements of a vector. For example, in the sequenceO = (45, −2, 800),O₃ refers to the third member of sequenceO, which is 800.

Also in mathematics and computing, a subscript can be used to represent theradix, or base, of a written number, especially where multiple bases are used alongside each other. For example, comparing values inhexadecimal,denary, andoctal one might write C_hex = 12_dec = 14_oct.

Subscripted numbers dropped below the baseline are also used for thedenominators of stackedfractions, like this:⁠67/68⁠.

The only common use of these subscripts is for the denominators of diagonal fractions^{[citation needed]}, like ½ or the signs forpercent %,permille ‰, andbasis point ‱. Certain standard abbreviations are also composed as diagonal fractions, such as ℅ (care of), ℀ (account of), ℁ (addressed to the subject), or in Spanish ℆ (cada uno/una, "each one").

These superscripts typically share a baseline withnumerator digits, the top of which are aligned with the top of the full-height numerals of the base font; lowercase ascenders may extend above.

Ordinal indicators are sometimes written as superscripts (1^st, 2^nd, 3^rd, 4^th, rather than 1st, 2nd, 3rd, 4th), although many English-languagestyle guides recommend against this use.^[4] Romance languages use a similar convention, such as 1^er or 2^e in French, or 4ª and 4º inGalician and Italian, or 4.ª and 4.º in Portuguese and Spanish.

In medieval manuscripts, many superscript as well as subscript signs were used to abbreviate text. From these developed moderndiacritical marks (glyphs, or "accents" placed above or below the letter). Also, in earlyMiddle High German,umlauts and other modifications to pronunciation would be indicated by superscript letters placed directly above the letter they modified. Thus the modernumlautü was written as uͤ. Both vowels and consonants were used in this way, as in ſheͨzze and boͮsen.^[5] In modern typefaces, these letters are usually smaller than other superscripts, and their baseline is slightly above the base font's midline, making them extend no higher than a typical ordinal indicator.

Superscripts are used for the standard abbreviations forservice mark (℠) andtrademark (™). The signs forcopyright © andregistered trademark ® are also sometimes superscripted, depending on the typeface or house style.

On handwritten documents and signs, a monetary amount may be written with the cents value superscripted, as in $8⁰⁰ or 8€⁵⁰. Often the superscripted numbers are underlined: $8⁰⁰, 8€⁵⁰. Thecurrency symbol itself may also be superscripted, as in^$80 or 6^¢.There is no ruling whether or not these characters need to be supercript, or made smaller than the numbers, or aligned to any of the various guide lines. That of course is decided by the preference of the typographer.

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Both low and high superscripts can be used to indicate the presence of afootnote in a document, like this⁵ or this.^xi Any combination of characters can be used for this purpose; in technical writing footnotes are sometimes composed of letters and numbers together, like this.^A.2 The choice of low or high alignment depends on taste, but high-set footnotes tend to be more common, as they stand out more from the text.

Inmathematics, high superscripts are used forexponentiation to indicate that one number or variable is raised to the power of another number or variable. Thusy⁴ isy raised to the fourth power, 2^x is 2 raised to the power ofx, and the equationE = mc² includes a term for thespeed of lightsquared. This led over time to an "abuse of notation" whereby superscripts indicate iterativefunction composition, includingderivatives. In an unrelated use, superscripts also indicate contravariant tensors inRicci calculus.

The charges ofions andsubatomic particles are also denoted by superscripts.Cl⁻ is a negatively chargedchlorine atom,Pb⁴⁺ is an atom oflead with a positive charge of four,e⁻ is anelectron,e⁺ is apositron, andμ⁺ is anantimuon.

Atomicisotopes are written using superscripts. In symbolic form, the number ofnucleons is denoted as a superscripted prefix to thechemical symbol (for example³
He
,¹²
C
,¹³
C
,¹³¹
I
, and²³⁸
U
). The lettersm orf may follow the number to indicate metastable or fissionisomers, as in^58m
Co
or^240f
Pu
.

Subscripts and superscripts can also be used together to give more specific information aboutnuclides. For example,²³⁵
₉₂U
denotes an atom ofuranium with 235 nucleons, 92 of which areprotons. A chemical symbol can be completely surrounded:¹⁴
₆C²⁺
₂ is a divalent cation ofcarbon with 14 nucleons, of which six are protons and 8 areneutrons, and there are two atoms in this chemical compound.

The numerators of stacked fractions (such as⁠34/35⁠) usually use high-set superscripts, although some specially designed glyphs keep the top of the numerator aligned with the top of the full-height numerals.

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This image shows the four common locations for subscripts and superscripts, according to their typical uses. The typeface isMinion Pro, set in Adobe Illustrator. Note that the default superscripting algorithms of most word processors would set the "th" and "lle" too high, and the weight of all the subscript and superscript glyphs would be too light.

Another minor adjustment that is often omitted by renderers is the control of the direction of movement^{[clarification needed]} for superscripts and subscripts, when they do not lie on the baseline. Ideally this should allow for the font, e.g. italics are slanting; most renderers adjust the position only vertically and do not also shift it horizontally. This may create a collision with surrounding letters in the same italic font size. One can see an example of such collision on the right side when rendered in HTML (see the figure on the right). To avoid this, it is often desirable to insert a small positive horizontal margin (or a thin space) (on the left side of the first superscript character), or a negative margin (or a tiny backspace) before a subscript. It is more critical with glyphs from fonts in Oblique styles that are more slanted than those from fonts in Italic style, and some fonts reverse the direction of slanting, so there is no general solution except when the renderer takes into account the font metrics properties that specifies the angle of slanting,

However the same problem occurs more generally between spans of normal glyphs (non-superscript and non-subscript) when slanting styles are mixed.

Many text editing andword processing programs have automatic subscripting and superscripting features, although these programs usually simply use ordinary characters reduced in size and moved up or down – rather than separately designed subscript or superscript glyphs. Professional typesetting programs such asQuarkXPress orAdobe InDesign also have similar features for automatically converting regular type to subscript or superscript. These programs, however, may also offer native OpenType support for the special subscript and superscript glyphs included in many professional typeface packages (such as those shown in the image above).

InHTML andWiki syntax, subscript text is produced by putting it inside the tags<sub> and</sub>. Similarly, superscripts are produced with<sup> and</sup>.^[7] The exact size and position of the resulting characters will vary by font and browser, but are usually reduced to around 75% original size.

InTeX's mathematics mode (as used inMediaWiki), subscripts are typeset with theunderscore, while superscripts are made with thecaret. Thus$X_{ab}$ produces${\displaystyle X_{ab}}$, and$X^{ab}$ produces${\displaystyle X^{ab}}$.

In LaTeX text mode the math method above is inappropriate, as letters will be in math italic, so the commandn\textsuperscript{th} will give n^th andA\textsubscript{base} will give A_base (textualsubscripts are rare, so\textsubscript is not built-in, but requires thefixltx2e package). As in other systems, when using UTF-8 encoding, the masculine º and feminine ª ordinal indicators can be used as characters, with no need to use a command.

In line with its origin as a superscript circle, thedegree symbol (°) is composed by a superscriptcircle operator (∘).^{\circ}.

Superscripts and subscripts of arbitrary height can be done with the\raisebox{<dimen>}{<text>} command: the first argument is the amount to raise, and the second is the text; a negative first argument will lower the text. In this case the text is not resized automatically, so a sizing command can be included, e.g.go\raisebox{1ex}{\large home}.

Unicode defines subscript and superscript characters in several areas; in particular, it has a full set of superscript and subscript digits. Owing to the popularity of using these characters to make fractions, most modern fonts render most or all of these as cap height superscripts and baseline subscripts. The same font may align letters and numbers in different ways. Other than numbers, the set of super- and subscript letters and other symbols is incomplete and somewhat random, and many fonts do not contain them. Because of these inconsistencies, these glyphs may not be suitable for some purposes (seeUses, above).

Several advanced features ofOpenType typefaces are supported for professionally designed subscript and superscript glyphs. Exactly which glyphs are included varies by typeface; some have only basic support for numerals, while others contain a full set of letters, numerals, and punctuation. They can be available via activatingsubs orsups feature tag. These feature tags can be turned on if software environment support optional features. In addition, some other typefaces placed them in a UnicodePrivate Use Area.

• Mathematical notation
• Superior letter
• Furigana
• Ruby character
• Typesetting
• Font
• Superscripts and Subscripts (Unicode block)
• Unicode subscripts and superscripts

• Bringhurst, Robert (2005),The Elements of Typographic Style, 3rd ed., Vancouver: Hartley and Marks,ISBN 0-88179-205-5.

Look upsubscript orsuperscript in Wiktionary, the free dictionary.

Look upAppendix:Subscript orAppendix:Superscript in Wiktionary, the free dictionary.

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• Vincent Connare's type-design standards for Microsoft
• Vertical alignment questionsArchived 2015-03-18 at theWayback Machine from Typophile

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