Ligature

A ligature is a single glyph that combines two or more letters into one unit. It is distinct from a digraph, which is simply two letters representing a single sound; a ligature is a single written symbol that may alter the appearance and spacing of its components.

Ligatures arose in handwritten manuscripts to prevent letter collisions and to improve readability. With movable type and later digital fonts, ligatures helped reduce gaps and ink leakage in printing. In Latin-script typography, common examples include fi and fl, as well as extended forms such as ffi and ffl. Some scripts also rely on ligature-like connections as an intrinsic feature of their writing system, such as certain Arabic or Indic scripts.

In modern digital typography, ligatures are implemented as substitutions within a font, controlled by font technology and software. OpenType, for example, supports a liga feature that enables standard ligatures, as well as contextual and stylistic variants. Font availability varies; some families include extensive ligature sets, while others offer only a few.

Unicode encodes several Latin ligatures as single code points, including fi (U+FB01), fl (U+FB02), ffi (U+FB03), and ffl (U+FB04), along with historic ligatures such as long s t (U+FB05) and s t (U+FB06). Usage can be automatic or manual, and some editors allow users to disable ligatures for specific contexts.