Numerical digit
From India, the thriving trade between Islamic sultans and Africa carried the concept to Cairo. Arabic mathematicians extended the system to include decimal fractions, and Muḥammad ibn Mūsā al-Ḵwārizmī wrote an important work about it in the 9th  century. The modern Arabic numerals were introduced to Europe with the translation of this work in the 12th century in Spain and Leonardo of Pisa's "Liber Abaci" of 1201. In Europe, the complete Indian system with the zero was derived from the Arabs in the 12th century.
Arabic numerals
In 825 Al-Khwārizmī wrote a treatise in Arabic, "On the Calculation with Hindu Numerals", which survives only as the 12th-century Latin translation, "Algoritmi de numero Indorum". "Algoritmi", the translator's rendition of the author's name, gave rise to the word "algorithm".