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.
Arabs
Other notable Arab contributions include among other things: establishing the science of chemistry by Jābir ibn Hayyān, establishing the science of cryptology and cryptanalysis by al-Kindi, the development of analytic geometry by Ibn al-Haytham, the discovery of the pulmonary circulation by Ibn al-Nafis, the discovery of the itch mite parasite by Ibn Zuhr, the first use of irrational numbers as an algebraic objects by Abū Kāmil, the first use of the positional decimal fractions by al-Uqlidisi, the development of the Arabic numerals and an early algebraic symbolism in the Maghreb, the Thabit number and Thābit theorem by Thābit ibn Qurra, the discovery of several new trigonometric identities by Ibn Yunus and al-Battani, the mathematical proof for Ceva's theorem by Ibn Hűd, the first accurate lunar model by Ibn al-Shatir, the invention of the torquetum by Jabir ibn Aflah, the invention of the universal astrolabe and the equatorium by al-Zarqali, the first description of the crankshaft by al-Jazari, the anticipation of the inertia concept by Averroes, the discovery of the physical reaction by Avempace, the identification of more than 200 new plants by Ibn al-Baitar the Arab Agricultural Revolution, and the Tabula Rogeriana, which was the most accurate world map in pre-modern times by al-Idrisi.