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 terms
subscript and
superscript, which are synonymous with the terms
inferior letter (or
number) and
superior letter (or
number), respectively. Most fonts that contain superscript/subscript will have predetermined size and orientation that is dependent on the design of the font.
Subscripts that are dropped below the baseline Subscripts are used in
chemical formulas. For example, the chemical formula for
glucose is
C6
H12
O6 (meaning that it is a molecule with 6
carbon atoms, 12
hydrogen atoms and 6
oxygen atoms). The chemical formula of the
water molecule, H2O, indicates that it contains two hydrogen atoms and one oxygen atom. A subscript is also used to distinguish between different versions of a
subatomic particle. Thus electron, muon, and tau
neutrinos are denoted and . A particle may be distinguished by multiple subscripts, such as for the
triple bottom omega 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
denominators of stacked
fractions, like this: .
Subscripts that are aligned with the baseline The only common use of these subscripts is for the denominators of diagonal fractions, like or the signs for
percent %,
permille ‰, and
basis 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").
Superscripts that typically do not extend above the ascender line These superscripts typically share a baseline with
numerator 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 (, , , , rather than 1st, 2nd, 3rd, 4th), although many English-language
style guides 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, or 4.ª and 4.º in
European Portuguese and
Spanish. In medieval manuscripts, many superscript as well as subscript signs were used to abbreviate text. From these developed modern
diacritical marks (
glyphs, 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.
Superscripts that typically extend above the ascender line Both low and high superscripts can be used to indicate the presence of a
footnote 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. 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
derivatives. In an unrelated use, superscripts also indicate contravariant tensors in
Ricci calculus. The charges of
ions 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
isotopes are written using superscripts. In symbolic form, the number of
nucleons 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
isomers, as in or . Subscripts and superscripts can also be used together to give more specific information about
nuclides. For example, denotes an atom of
uranium with 235 nucleons, 92 of which are
protons. A chemical symbol can be completely surrounded: is a divalent cation of
carbon with 14 nucleons, of which six are protons and 8 are
neutrons, 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. ==Alignment examples==