Special feature: used to present user with choice all alternate forms of the character
Replaces the above-base part of a vowel sign. For Khmer and similar scripts.
Positions a mark glyph above a base glyph.
Ligates a consonant with an above-mark.
Converts figures separated by slash with alternative stacked fraction form
Hindi for unbreakable.  Ligates consonant+halant+consonant, usually only for k-ss and j-ny combinations.
Replaces halant+consonant combination with a subscript form.
Positions a mark glyph below a base glyph
Ligates a consonant with a below-mark.
Substitutes capital letters with petite caps
Substitutes capital letters with small caps
Applies a second substitution feature based on a match of a character pattern within a context of surrounding patterns
Replace characters, especially punctuation, with forms better suited for all-capital text, cf. titl
Either calls a ligature replacement on a sequence of characters or replaces a character with a sequence of glyphs. Provides logic that can for example effectively alter the order of input characters.
Khmer
Ligates consonant+halant+consonant, indicates part of a conjunct.
Applies a second ligature feature based on a match of a character pattern within a context of surrounding patterns
Positions punctuation marks vertically and horizontally
Adjusts spacing between letters in all-capitals text
Converts letter to a swashed version based on characters around the letter
Precise positioning of a letter's connection to an adjacent one
Multiple variants of a single character, which may not apply to many other characters, see references for voluminous documentation
Adjusts horizontal positioning between glyphs. (Always enabled, as opposed to 'kern'.)
Ligatures to be applied at the user's discretion
Converts to appropriate fraction denominator form, invoked by frac
Typographic alternatives for some Japanese tetragrams
Replaces final glyph on the line with an alternate
Syriac
Syriac
Substitutes a special form of a letter at end of words (required by Arabic and Syriac)
Converts figures separated by slash with diagonal fraction
Substitutes proportionally spaced character with full-width versions (esp. for Latin letters within Chinese)
Replaces consonant+halant with a half form, indicating it is part of a conjunct.
Replaces a glyph for final consonant+halant.
Re-positions full-width glyphs on half-width spaces
Obsolete forms of characters to be applied at the user's discretion, cf. hlig
Alternate forms for horizontal kana text, e.g. ー for chōonpu instead of ｜, cf. vkna
Obsolete ligatures to be applied at the user's discretion
Transliterates Chinese-style characters with Korean Hangul
Hojo alternates for Japanese tetragrams
Substitutes uniformly-spaced characters with half-width version
Substitutes a special form of a letter occurring at the beginning of a word (required by Arabic and Syriac)
Substitutes a special form of a letter occurring outside a word (required by Arabic and Syriac)
Replaces letter with corresponding italic glyph
User selectable wider and narrower alternates, used especially for justifying
JIS 2004 alternates for Japanese tetragrams, not accessible per Unicode
JIS C 6226-1978 alternates for Japanese tetragrams, not accessible per Unicode
JIS X 0208-1983 alternates for Japanese tetragrams, not accessible per Unicode
JIS X 0208-1990 alternates for Japanese tetragrams, not accessible per Unicode
Fine horizontal positioning of one glyph to the next, based on the shapes of the glyphs
Re-positions glyphs at end of line. Called by opbd.
Replaces (by default) sequence of characters with a single ligature glyph
Initial group of consonants for a synthesized Korean Hangul tetragram
Replaces numerals with glyphs meant to fit better in all-capitals text, often also tnum
Substitutes character with the preferred form based on script language
Replaces characters with forms befitting left-to-right presentation (except mirrored forms)
Replaces characters with possibly mirrored forms befitting left-to-right presentation
Fine positioning of a mark glyph to a base character
Syriac
Substitutes a special form of letters between other letters in words (required by Arabic and Syriac)
Replaces Greek characters with special forms for use in mathematics
Fine positioning of a mark glyph to another mark character
Used in Windows 95 for positioning of Arabic marks
Provides user access to circled digits, inverse letters etc.
NLC alternates for Japanese tetragrams
Replace consonant+nukta (dot mark) with single glyph.
Converts to appropriate fraction numerator form, invoked by frac
Replaces numerals with cased old-style numerals, often also pnum
Re-positions glyphs at beginning and end of line, for precise justification of text.
Replaces characters with ordinal forms for use after numbers
Decorative alternates for the bullet character •
Re-positions otherwise monospace characters according to glyph width
Substitute lower-case letters with their petite caps analogs
Kana for use alongside alphabets, without grid typography
Replaces numerals with glyphs of proportional width, often also onum
Replaces halant+consonant at the end of a consonant cluster with a glyph at the beginning. Khmer, Myanmar, Malayalam, Telugu
Ligates consonant combinations.
Substitutes final halant+consonant with special form.  Khmer and Gurmukhi, Malayalam
Ligates a final consonant+consonant.
Replaces uniformly-spaced glyphs with proportional ones
Replaces uniformly-spaced glyphs with quarter-width ones (punctuation etc.)
Replaces character with random forms (meant to simulate handwriting)
Contextual alternates required for correct text display which differs from the default join for other letters, required especially important by Arabic
Replaces halant+ra with a rakar glyph, indicating it is part of a conjunct.
Ligatures required for correct text display (any script, but in cursive)
Replaces initial ra+halant with a final reph mark, indicating part of a conjunct.
Re-positions glyphs at beginning of line. Called by opbd.
Replaces characters with forms befitting right-to-left presentation (except mirrored forms)
Replaces characters with possibly mirrored forms befitting right-to-left presentation
Ruby characters, small print
Special variants of a single character, which need apply to specific font variation, required by variable fonts
Either replaces with, or displays list of, stylistic alternatives for a character
as in "H2O", "SOx" or "YCbCr" (but using the same font weight and predefined position in contrast these plain HTML subs and sups)
Not a lookup: feature's table provides to applications information about the appearance and intent of the font, to aid in font selection.
Substitutes lower-case letters with small caps versions
Replaces sinograms with their simplified versions, may be language dependent
Replaces character with one from a font-specific set of stylistic alternatives
Substitutes a special form of a stretchy glyph onto one or more letters (required by Syriac)
Replaces character with subscript version, cf. numr
Replaces character with superscript version, cf. dnom
Either replaces character with or displays multiple swashed versions
Replaces characters with forms suited for large type, as in titles
Final group of consonants for a synthesized Korean Hangul tetragram
Japanese alternates for proper names
Replaces numerals with glyphs of uniform width, often also lnum
Replaces Chinese characters with their traditional versions
Substitutes uniformly-spaced character with a version of 1/3 width (punctuation, etc.)
Replaces lowercase and uppercase letters with a set of single case glyphs
Positions shorter characters to be centered vertically with full-height characters
Replaces consonant+rakar combinations with a vattu variant ligature.
A subset of vrt2: prefer the latter feature
Positions characters to be centered vertically with half-height characters
Medial group of vowels for a synthesized Korean Hangul tetragram
Alternate Japanese kana forms for vertical text, e.g. ｜ for chōonpu instead of ー, cf. hkna
Fine vertical positioning of characters based on shape
Re-positions glyphs vertically to be centered on proportional full-height characters
Replaces characters with forms suitable for vertical writing, possibly by rotating 90°
Replaces characters with forms suitable for vertical writing, possibly by shifting or shape
Replaces 0 figure with slashed 0