Thuluth script made its first appearance in the fourth century hegira (11th Century AD). Thuluth means "one third" and the script is characterized by one third of each letter sliding downward. It is a large and elegant cursive script, used in medieval times in mosque decorations and for writing sura headings in the Qur’an.

Thuluth has oblique lines and is usually written in ample curves. An important aspect of Thuluth script is the use of harakat (marks used to represent vowel sounds) and other marks to make the script more beautiful. In the 13th Century, Thuluth took on the ornamental role formerly associated with the  script. Several other calligraphic styles evolved from Thuluth through slight changes of form.