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A subscript or superscript 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 the baseline, while superscripts are above. Subscripts and superscripts are perhaps most often used in , mathematical expressions, and specifications of chemical compounds and , but have many other uses as well.
In professional typography, 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 letter" and "inferior" letters, figures, etc., or just "superiors" and "inferiors". In English, most nontechnical use of superiors is archaic.Bringhurst 2005, pp. 311–312. Superior and inferior figures on the baseline are used for and most other purposes, while lowered inferior figures are needed for chemical and mathematical subscripts.Bringhurst 2005, p. 309.
A subscript is also used to distinguish between different versions of a subatomic particle. Thus electron, muon, and tau are denoted and . A particle may be distinguished by multiple subscripts, such as for the Omega baryon particle.
Similarly, subscripts are also used frequently in mathematics to define different versions of the same variable: for example, in an equation x0 and xf might indicate the initial and final value of x, while vrocket and vobserver 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").
Subscripts are often used to refer to members of a mathematical sequence or set or elements of a vector. For example, in the sequence O = (45, −2, 800), O3 refers to the third member of sequence O, which is 800.
Also in mathematics and computing, a subscript can be used to represent the radix, or base, of a written number, especially where multiple bases are used alongside each other. For example, comparing values in hexadecimal, denary, and octal one might write Chex = 12dec = 14oct.
Subscripted numbers dropped below the baseline are also used for the of stacked , like this: .
Ordinal indicators are sometimes written as superscripts (, , , , rather than 1st, 2nd, 3rd, 4th), although many English-language recommend against this use. Romance languages use a similar convention, such as 1er or 2e in French, 4ª and 4º in Galician, Brazilian Portuguese and Italian language, or 4.ª and 4.º in European Portuguese and Spanish language.
In medieval manuscripts, many superscript as well as subscript signs were used to abbreviate text. From these developed modern (, or "accents" placed above or below the letter). Also, in early Middle High German, umlauts and other modifications to pronunciation would be indicated by superscript letters placed directly above the letter they modified. Thus the modern umlaut ü was written as uͤ. Both vowels and consonants were used in this way, as in ſheͨzze and boͮsen. 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 for service mark () and trademark (). The signs for copyright © and registered 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 $ or . Often the superscripted numbers are underlined: $, ⁵⁰. The currency symbol itself may also be superscripted, as in .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.
In mathematics, high superscripts are used for exponentiation to indicate that one number or variable is raised to the power of another number or variable. Thus y4 is y raised to the fourth power, 2 x is 2 raised to the power of x, and the equation includes a term for the speed of light squared. This led over time to an "abuse of notation" whereby superscripts indicate iterative function composition, including . In an unrelated use, superscripts also indicate contravariant tensors in Ricci calculus.
The charges of and subatomic particles are also denoted by superscripts. is a negatively charged chlorine atom, is an atom of lead with a positive charge of four, is an electron, is a positron, and is an antimuon.
Atomic are written using superscripts. In symbolic form, the number of is denoted as a superscripted prefix to the chemical symbol (for example , , , , and ). The letters m or f may follow the number to indicate metastable or fission nuclear isomer, as in or .
Subscripts and superscripts can also be used together to give more specific information about . For example, denotes an atom of uranium with 235 nucleons, 92 of which are . A chemical symbol can be completely surrounded: is a divalent cation of carbon with 14 nucleons, of which six are protons and 8 are , and there are two atoms in this chemical compound.
The numerators of stacked fractions (such as ) 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.
| Default subscript and superscript rendered in HTML for fonts in normal styles | Example of possible collision of italic styles in HTML |
Another minor adjustment that is often omitted by renderers is the control of the direction of movement 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.
| + Comparison of software support | |||||||
| OpenOffice.org 3.3 | style="text-align:center;" | 58% | −33% | +33% | style="text-align:center;" | ||
| LibreOffice 5.3 | style="text-align:center;" | 58% | −33% | +33% | style="text-align:center;" | ||
| Microsoft Word 2015 | style="text-align:center;" | 50% | −14.1% | +40% | Manual | ||
| Adobe Illustrator CS3 | style="text-align:center;" | 58.3% | −33.3% | +33.3% | style="text-align:center;" | ||
| Adobe Photoshop CS3 | Ordinal indicators only | 58.3% | −33.3% | +33.3% | Manual | ||
| LaTeX | style="text-align:center;" (using XeLaTeX or LuaTeX only) | ≈70% | −14% | +25% | Manual | ||
| Notes: | |||||||
In LaTeX text mode the math method above is inappropriate, as letters will be in math italic, so the command n\textsuperscript{th} will give nth and A\textsubscript{base} will give Abase (textual subscripts are rare, so \textsubscript is not built-in, but requires the fixltx2e 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, the degree symbol (°) is composed by a superscript circle 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}.
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