The "normal" digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 are often called Arabic digits (especially to distinguish them from Roman numerals like XIV). In fact, Western Europeans adopted them from the Arabs, who had adopted them from scripts used in India. In these processes, the shapes of digits changed, however. The digits used in Arabic writing have shapes which differ from those of these "Arabic" digits, and they are classified as separate characters in Unicode: they are "Arabic-Indic digits" in block Arabic. There are also several other sets of digits in Unicode, for use in different scripts.
In Unicode, there are distinct characters for digits used as superscripts or subscripts. Only the superscripts corresponding to 1, 2 and 3, that is ¹ and ² and ³, belong to ISO Latin 1; the others are in block Superscripts and Subscripts in Unicode. Notice that ISO Latin 1 repertoire contains two characters which may look like superscript 0: the degree sign (°) and the masculine ordinal indicator (º).
When using the ISO Latin character repertoire only, it is probably
best to use superscript
¹ or
² or
³
only if all superscripts used in a document can be expressed that
way. Otherwise, i.e. when you need to use some other method for presenting
other superscripts (such as the
SUP
element when authoring in
HTML), it is probably best to use that method throughout,
for uniformity.
The so-called vulgar fractions are characters denoting fractional numbers as single characters. In ISO Latin 1, there are such characters for the fractions 1/4, 1/2, 3/4 (namely ¼ ½ ¾). This reflects the character repertoire on many typewriters. Depending on the font, the bar (which corresponds to fraction slash) can be horizontal or slanted.
Analogously with the situation with
superscript digits,
when using the ISO Latin 1 character repertoire only,
it is probably
best to use vulgar fractions
only if all fractions used in a document can be expressed that
way. Otherwise, i.e. when you need to use some other method for presenting
other fractions
it is probably best to use that method throughout,
for uniformity.
You could use simply expressions like 2/3 and 1/4.
(In the
HTML language,
you might use the
SUP
markup for the nominator
and the
SUB
markup for the denominator,
thereby suggesting a presentation which somewhat resembles
vulgar fractions in appearance. However, such markup may cause
uneven line spacing. See also section
Fractions
in
Math in HTML.)
A practical problem with the vulgar fraction characters is that their appearance is often hard to read, especially on computer screens.
In Unicode, both the superscripts and the vulgar fractions are compatibility characters, so that e.g. the compatibility decomposition of ¾ is 3/4 presented in "fraction style".