Access All AlternatesThis feature makes all variations of a selected character accessible. This serves several purposes: An application may not support the feature by which the desired glyph would normally be accessed; the user may need a glyph outside the context supported by the normal substitution, or the user may not know what feature produces the desired glyph. Since many-to-one substitutions are not covered, ligatures would not appear in this table unless they were variant forms of another ligature.
Discretionary LigaturesReplaces a sequence of glyphs with a single glyph which is preferred for typographic purposes. This feature covers those ligatures which may be used for special effect, at the user's preference.
DenominatorsReplaces selected figures which follow a slash with denominator figures.
FractionsReplaces figures separated by a slash with 'common' (diagonal) fractions.
Historical FormsSome letterforms were in common use in the past, but appear anachronistic today. The best-known example is the long form of s; others would include the old Fraktur k. Some fonts include the historical forms as alternates, so they can be used for a 'period' effect. This feature replaces the default (current) forms with the historical alternates. While some ligatures are also used for historical effect, this feature deals only with single characters.
KerningAdjusts amount of space between glyphs, generally to provide optically consistent spacing between glyphs. Although a well-designed typeface has consistent inter-glyph spacing overall, some glyph combinations require adjustment for improved legibility. Besides standard adjustment in the horizontal direction, this feature can supply size-dependent kerning data via device tables, "cross-stream" kerning in the Y text direction, and adjustment of glyph placement independent of the advance adjustment. Note that this feature may apply to runs of more than two glyphs, and would not be used in monospaced fonts. Also note that this feature does not apply to text set vertically.
Standard LigaturesReplaces a sequence of glyphs with a single glyph which is preferred for typographic purposes. This feature covers the ligatures which the designer/manufacturer judges should be used in normal conditions.
NumeratorsReplaces selected figures which precede a slash with numerator figures, and replaces the typographic slash with the fraction slash.
OrdinalsReplaces default alphabetic glyphs with the corresponding ordinal forms for use after figures. One exception to the follows-a-figure rule is the numero character (U+2116), which is actually a ligature substitution, but is best accessed through this feature.
OrnamentsThis is a dual-function feature, which uses two input methods to give the user access to ornament glyphs (e.g. fleurons, dingbats and border elements) in the font. One method replaces the bullet character with a selection from the full set of available ornaments; the other replaces specific "lower ASCII" characters with ornaments assigned to them. The first approach supports the general or browsing user; the second supports the power user.
Stylistic AlternatesMany fonts contain alternate glyph designs for a purely esthetic effect; these don't always fit into a clear category like swash or historical. As in the case of swash glyphs, there may be more than one alternate form. This feature replaces the default forms with the stylistic alternates.
Scientific InferiorsReplaces lining or oldstyle figures with inferior figures (smaller glyphs which sit lower than the standard baseline, primarily for chemical or mathematical notation). May also replace lowercase characters with alphabetic inferiors.
Stylistic Set 1In addition to, or instead of, stylistic alternatives of individual glyphs (see 'salt' feature), some fonts may contain sets of stylistic variant glyphs corresponding to portions of the character set, e.g. multiple variants for lowercase letters in a Latin font. Glyphs in stylistic sets may be designed to harmonise visually, interract in particular ways, or otherwise work together. Examples of fonts including stylistic sets are Zapfino Linotype and Adobe's Poetica. Individual features numbered sequentially with the tag name convention 'ss01' 'ss02' 'ss03' . 'ss20' provide a mechanism for glyphs in these sets to be associated via GSUB lookup indexes to default forms and to each other, and for users to select from available stylistic sets.
SubscriptThe "subs" feature may replace a default glyph with a subscript glyph, or it may combine a glyph substitution with positioning adjustments for proper placement.
SuperscriptReplaces lining or oldstyle figures with superior figures (primarily for footnote indication), and replaces lowercase letters with superior letters (primarily for abbreviated French titles).
SwashThis feature replaces default character glyphs with corresponding swash glyphs. Note that there may be more than one swash alternate for a given character.
