Ligatures
الرُبط
When letters merge into a single combined form
A ligature is a combined glyph formed when two or more letters merge into a single shape. In Arabic, some ligatures are mandatory — most notably لا (lam-alef), which must always be rendered as a single form, never as two separate letters. Other ligatures are optional and stylistic, appearing more frequently in calligraphic or display typefaces.
Mandatory vs. Stylistic
Unlike Latin, where ligatures like "fi" and "fl" are decorative refinements, Arabic's mandatory ligatures are part of the script's orthographic rules. Breaking a لا ligature is considered a typographic error. Beyond mandatory forms, Arabic typefaces — especially those inspired by Thuluth, Nastaliq, or Diwani — can include hundreds of optional ligatures that create denser, more calligraphic textures. The range of ligatures in a font is one of the strongest signals of its typographic quality.