nonjoiner

NonJoiner is a term used in typography and digital text to describe letters or characters that do not connect to the following letter in certain cursive scripts, most notably Arabic. In the Arabic writing system, most letters are connected in a flowing, contextual shape, but a small set of letters do not join to the letter that comes after them. The primary non-joining letters are Alef (ا), Dal (د), Dhal (ذ), Ra (ر), Zay (ز), and Waw (و). Variants of Alef, such as Alef with Hamza above or below, are also treated as non-joining in terms of script behavior. These letters can connect to the preceding letter if that preceding letter is a joining letter, but they prevent connection to the next letter, effectively creating a boundary in the cursive word.

In typography and font rendering, the concept of non-joiners influences how letters take their shapes within a sequence. The presence of a non-joining letter alters the joining state machine used by shaping engines, which in turn determines which contextual form (initial, medial, final, or isolated) a letter will adopt. Correct handling of non-joiners is essential for accurate display of Arabic, Persian, Urdu, and other Arabic-script texts.

Unicode and digital text introduce explicit mechanisms to control joining behavior. The Zero Width Non-Joiner (U+200C) is a non-printing character used to prevent two characters from joining across a boundary, while the Zero Width Joiner (U+200D) does the opposite. These characters help manage ligatures, mixed-script runs, and precise text layouts.

See also: Zero Width Non-Joiner, Zero Width Joiner, Arabic script shaping, non-joining letters.