Ligatura

Ligature, or ligatura, is a term with several meanings. In typography, a ligature is a single glyph that combines two or more letters into one symbol, often to reflect their connected pronunciation or to improve readability. The word derives from the Latin ligatura, meaning binding or tying.

In typography, common ligatures include fi, fl, and the ae/oe combinations æ and œ. There are standard ligatures, which are usually available in a font, and discretionary ligatures, which are optional and used for stylistic effect. Some scripts employ contextual ligatures that change depending on neighboring letters. Digital fonts implement ligatures through features such as OpenType liga for standard ligatures, dlig for discretionary ligatures, and calt for contextual alternates.

In medicine, a ligature refers to the act of tying a blood vessel or duct with a thread or other material to stop bleeding or seal a passage. This is a common surgical technique used in procedures such as cesarean delivery, gastrointestinal surgery, and vascular operations. Ligatures can be non-absorbable or absorbable; methods include simple ligatures and transfixion ligatures. Potential risks include infection, tissue damage, and slippage. Advances in hemostasis and energy devices have reduced reliance in some settings, but ligatures remain essential in many operations.

Ligature is also used in other domains, such as historical music notation to denote a group of notes tied together. In general usage, the term highlights the act of binding or tying, whether for securing a structure, a flow of blood, or a sequence of musical notes. In typography, ligature usage varies by language and font, and may be automatically applied or disabled depending on the design.