Glyph Substitution

A typographic process in which one or more characters in a text are replaced with alternative visual forms (glyphs) based on context, language, or stylistic requirements. In OpenType fonts, the GSUB table defines rules for substitutions such as ligatures (combining two characters into one glyph), contextual alternates, and script-specific forms. Glyph substitution is essential for correctly rendering complex scripts like those used in Indian languages, where consonant conjuncts require combining multiple characters into a single visual form. For accessibility, correct glyph substitution ensures that screen readers and Braille translation systems can map between the visual representation and the underlying character sequence.